CUET UG Applied Mathematics Booster Test 2 - Applications of Derivatives
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QUESTION 1 OF 20
Applying the second derivative test to find the local extrema of the polynomial f(x) = 4x^3/3 + 6x^2 + 8x + 7, evaluating the second derivative at the critical point x = -2 yields f''(-2) = -4. This mathematically confirms that x = -2 is strictly a:
QUESTION 2 OF 20
Match the critical points of f(x) = x^3 - 3x^2 + 3x + 5 to their evaluated extremum properties.
| List I | List II |
|---|---|
| 1. f'(1) | a. Strictly > 0 |
| 2. f''(1) | b. Exactly 0 |
| 3. Left neighbourhood of 1, f'(x) | c. Strictly > 0 (maintains positive sign) |
| 4. Right neighbourhood of 1, f'(x) | d. Evaluates to 0, implying test failure |
QUESTION 3 OF 20
Which of the following strict mathematical statements regarding absolute extrema on closed vs open intervals are universally TRUE?
1) A function f defined in a closed interval may have a local extremum value even at the boundary points.
2) Not every critical point inside an open interval is definitively a point of local extremum.
3) A function f defined in an open interval will have a local extremum value exclusively at a critical point.
4) Absolute extrema cannot exist on any unbounded interval (–∞, ).
QUESTION 4 OF 20
Identify the incorrect analytical statement regarding the absolute extrema of the linear function f(x) = 2x + 5 evaluated strictly on the open interval (-2, 4).
QUESTION 5 OF 20
The graph of the fractional power function f(x) = x^(2/3) possesses a critical point behaviour at x = 0 where f'(0) is algebraically not defined. Geometrically, this specific non-differentiable point is strictly classified as a:
QUESTION 6 OF 20
A smooth turning curve like f(x) = |x| + 3 possesses a critical point at x = 0. Since the derivative f'(0) is fundamentally undefined due to differing left and right limits, the geometric feature explicitly present at (0,3) is a:
QUESTION 7 OF 20
In rigorous optimization using derivatives, if the second derivative test yields f''(c) = 0 at a confirmed critical point 'c', the absolute mandatory next step is to:
QUESTION 8 OF 20
During objective function analysis for the wire cut into a square and a circle (Total length = 40), the combined area A(x) features a second derivative A''(x). Evaluated analytically, A''(x) strictly equals:
QUESTION 9 OF 20
A manufacturer's profit-related condition requires finding the absolute maximum profit. Given P(x) = -9x² + 522x - 2500, evaluating P(29) mathematically yields an absolute maximum weekly profit of:
QUESTION 10 OF 20
Based on the marginal equality principle, a firm's Marginal Cost (MC) is proven to fall continuously as output 'x' increases ONLY if the derivative of the Marginal Cost with respect to 'x' (d(MC)/dx) strictly resides in which region?
QUESTION 11 OF 20
A printed page must contain 180 sq cm of text with margins. The total area function is A(x) = xy + 5x + 4y + 20. By substituting y = 180/x, solving A'(x) = 0 for the most economical dimension 'x' yields:
QUESTION 12 OF 20
For minimum distance/area optimization where a 40m wire is divided, the precise length of the second piece of wire formed strictly into a circle is algebraically evaluated as:
QUESTION 13 OF 20
QUESTION 14 OF 20
QUESTION 15 OF 20
In real-life change models involving geometric expansion, the rate of change of volume of a sphere strictly with respect to its surface area (dV/dS) evaluated exactly at a radius r = 5 m equates to:
QUESTION 16 OF 20
In production and demand analysis, a firm establishes its linear price-demand relationship. If the firm sells 1400 units at ₹4 and 1800 units at ₹2, the derived linear price function p(x) strictly evaluates to:
QUESTION 17 OF 20
Using tangent-based interpretation, find the explicit slope of the tangent to the curve y = (x^3 - 1)(x - 2) evaluated exactly at the point where it cuts the x-axis at (1,0).
QUESTION 18 OF 20
In gradient applications, the implicit curve x^(2/3) + y^(2/3) = 2 features a tangent at the coordinate (1, 1). The corresponding equation of the normal line strictly evaluates to:
QUESTION 19 OF 20
In derivative-based modelling, the Marginal Cost (MC) equation for a firm is explicitly derived from C(x) = x^2 + 30x + 1500. The exact numerical MC evaluated at a production level of 20 toys is:
QUESTION 20 OF 20
In applied mathematical problems involving higher-order polynomial curves, the specific curve y = 4x^3 - 2x^5 possesses tangents that strictly pass through the geometric origin (0,0). The valid x-coordinates of the points of contact are exactly:
Test Complete!
Answer Review
1 Applying the second derivative test to find the local extrema of the polynomial f(x) = 4x^3/3 + 6x^2 + 8x + 7, evaluating the second derivative at the critical point x = -2 yields f''(-2) = -4. This mathematically confirms that x = -2 is strictly a:
Second derivative test decides concavity Negative value implies concave down Concave down at critical point → local maximum
At a critical point: If f''(c) < 0 → function is concave downward Concave downward at x = -2 implies peak behavior Hence x = -2 is a local maximum point.
- A → requires f''(c) > 0
- C → inflexion requires sign change of concavity
- D → discontinuity is unrelated to derivatives
Used: Extreme Word Filter
Application: Spotting the negative evaluation distinguishes local peaks from minima, rapidly eliminating unrelated discontinuous or inflexion-based mathematical behaviors.
Final Logic: f''(c) < 0 ⇒ concave down ⇒ local maximum
"Minus second derivative = peak"
2 Match the critical points of f(x) = x^3 - 3x^2 + 3x + 5 to their evaluated extremum properties.
| List I | List II |
|---|---|
| 1. f'(1) | a. Strictly > 0 |
| 2. f''(1) | b. Exactly 0 |
| 3. Left neighbourhood of 1, f'(x) | c. Strictly > 0 (maintains positive sign) |
| 4. Right neighbourhood of 1, f'(x) | d. Evaluates to 0, implying test failure |
f'(x) = 3(x−1)² No sign change at x=1 Indicates stationary inflexion behavior
At x=1: derivative does not change sign → (II) f''(1)=0 → neutral second derivative behavior Thus correct matching follows A-II, B-IV, C-I, D-III.
- A → incorrect mapping of sign change
- B → mismatches derivative behavior
- D → swaps extremum interpretation
Used: Option Grouping
Application: Grouping the universally positive neighborhood derivative behaviors quickly isolates the single correct structural pairing, preventing mapping confusion entirely.
Final Logic: derivative no sign change ⇒ correct classification
"No sign change = no extremum"
3 Which of the following strict mathematical statements regarding absolute extrema on closed vs open intervals are universally TRUE?
1) A function f defined in a closed interval may have a local extremum value even at the boundary points.
2) Not every critical point inside an open interval is definitively a point of local extremum.
3) A function f defined in an open interval will have a local extremum value exclusively at a critical point.
4) Absolute extrema cannot exist on any unbounded interval (–∞, ).
Closed interval allows boundary extrema Critical points may or may not be extrema Open intervals do not guarantee extrema
1 true: boundary points can be extrema 2 true: critical point not always extremum 3 true: extrema occur at critical points or boundaries 4 false: extrema can exist on unbounded intervals (e.g., parabola minimum)
- 4 → incorrect universal claim
Used: Elimination
Application: Eliminating the clearly false unbounded claim immediately rules out incorrect combinations, perfectly isolating the correct universally true mathematical statements.
Final Logic: only 1,2,3 satisfy all conditions
"Endpoints + critical points = extrema check"
4 Identify the incorrect analytical statement regarding the absolute extrema of the linear function f(x) = 2x + 5 evaluated strictly on the open interval (-2, 4).
Linear function increases on interval Open interval does not include endpoints Hence no max/min attained
Even though limit at x→4 gives 13, it is not attained inside open interval → so no absolute maximum exists.
- A → true
- B → true
- D → true
Used: Extreme Word Filter
Application: Highligting the absolute terminology instantly flags the functionally unattained maximum on the open interval, perfectly resolving boundary condition confusion.
Final Logic: open interval ⇒ endpoint value not attained
"Open interval = no endpoint value"
5 The graph of the fractional power function f(x) = x^(2/3) possesses a critical point behaviour at x = 0 where f'(0) is algebraically not defined. Geometrically, this specific non-differentiable point is strictly classified as a:
Derivative undefined at 0 Sharp point behavior Not smooth
At x=0: derivative undefined curve has sharp point with steep change Thus classified as cusp.
- A → not smooth
- B → concavity change not applicable
- D → function defined at 0
Used: Contextual Matching
Application: Properly matching the algebraically undefined mathematical derivative specifically with its sharply pointed geometric behavior immediately excludes smoothly turning alternatives.
Final Logic: non-smooth sharp point ⇒ cusp
"Sharp tip = cusp"
6 A smooth turning curve like f(x) = |x| + 3 possesses a critical point at x = 0. Since the derivative f'(0) is fundamentally undefined due to differing left and right limits, the geometric feature explicitly present at (0,3) is a:
Left and right derivatives differ Sharp bend at origin Continuous but not differentiable
At x=0: slope from left = -1 slope from right = +1 → forms a corner point.
- A → cusp involves infinite slope
- C → no horizontal tangent
- D → no concavity change
Used: Elimination
Application: Rapidly eliminating infinite cusp and smooth inflexion attributes confirms a corner point by directly addressing differing constant finite slopes.
Final Logic: piecewise slope mismatch ⇒ corner
"Different slopes = corner"
7 In rigorous optimization using derivatives, if the second derivative test yields f''(c) = 0 at a confirmed critical point 'c', the absolute mandatory next step is to:
Second derivative test inconclusive Need sign analysis Check f'(x) behavior
When f''(c)=0: second derivative test fails must use first derivative sign change test
- A → not justified
- B → not justified
- D → unrelated
Used: Elimination
Application: Systematically removing completely unjustified extremum conclusions for a zero derivative perfectly highlights the strictly mandatory fallback to first derivative testing.
Final Logic: f''=0 ⇒ switch to first derivative test
"Zero second derivative → change test"
8 During objective function analysis for the wire cut into a square and a circle (Total length = 40), the combined area A(x) features a second derivative A''(x). Evaluated analytically, A''(x) strictly equals:
Differentiate area twice Apply constraint expression Simplify constants
From A(x), differentiation yields constant second derivative terms: A''(x)=1/8 + 1/(2π)
- B → incorrect scaling
- C → incorrect coefficient
- D → dimensionally invalid
Used: Substitution
Application: Substituting precise constraint values strictly into the combined algebraic equation quickly verifies the exact constant curvature without secondary calculation confusion.
Final Logic: correct differentiation yields A''(x) expression
"Second derivative = constant curvature"
9 A manufacturer's profit-related condition requires finding the absolute maximum profit. Given P(x) = -9x² + 522x - 2500, evaluating P(29) mathematically yields an absolute maximum weekly profit of:
Vertex gives maximum Substitute x=29 Evaluate expression
P(29)= -9(841)+522(29)-2500 = -7569+15138-2500 = 5069
- A → too low
- C → miscalculated
- D → inflated value
Used: Substitution
Application: Directly substituting the specifically evaluated vertex explicitly yields the precise absolute profit figure, seamlessly bypassing lengthy secondary theoretical quadratic analyses.
Final Logic: plug vertex x into profit function
"Vertex gives peak profit"
10 Based on the marginal equality principle, a firm's Marginal Cost (MC) is proven to fall continuously as output 'x' increases ONLY if the derivative of the Marginal Cost with respect to 'x' (d(MC)/dx) strictly resides in which region?
MC decreasing means negative slope derivative of MC negative implies downward trend
If d(MC)/dx < 0: MC decreases as x increases
- A → increasing
- B → constant
- D → undefined behavior
Used: Extreme Word Filter
Application: Isolating the explicitly necessary negative gradient requirement perfectly defines the downward slope, instantly eliminating constant, increasing, or undefined alternatives.
Final Logic: negative derivative ⇒ decreasing function
"Negative slope = falling curve"
11 A printed page must contain 180 sq cm of text with margins. The total area function is A(x) = xy + 5x + 4y + 20. By substituting y = 180/x, solving A'(x) = 0 for the most economical dimension 'x' yields:
Substitute constraint y = 180/x Differentiate A(x) Solve A'(x)=0 gives x=12
The area function becomes: A(x) = x(180/x) + 5x + 4(180/x) + 20 = 180 + 5x + 720/x + 20 Differentiate: A'(x) = 5 - 720/x² Set A'(x)=0: 5 = 720/x² → x² = 144 → x = 12 Thus, optimal dimension is 12 cm.
- Option A → does not satisfy derivative condition
- Option C → does not satisfy x² = 144
- Option D → too large, violates extremum condition
Used: Elimination
Application: Only x satisfying A'(x)=0 is valid; others fail equation check.
Final Logic: Critical point from derivative equation uniquely gives x=12.
"720/5 = 144 → √144 = 12"
12 For minimum distance/area optimization where a 40m wire is divided, the precise length of the second piece of wire formed strictly into a circle is algebraically evaluated as:
Form area function Differentiate Solve gives optimal split
Let square side be x ⇒ perimeter = 4x Circle wire = 40 − 4x Radius r = (40 − 4x)/(2π) Minimizing total area: A(x) = x² + πr² Solving A'(x)=0 gives: x = 160/(π+4) Thus circle length: 40 − 4x = 40π/(π+4)
- Option B → corresponds to square part, not circle length
- Option C → dimensionally inconsistent
- Option D → incorrect scaling factor
Used: Option Grouping
Application: Correctly partitioning the total wire length based on the optimization derivative ensures the circle piece matches the required length.
Final Logic: Correct partition of wire gives circle length = 40π/(π+4)
"Circle part always carries π in numerator"
13
Substitute the first equation \(3h^{2}-k^{2}=8\) into the second. \(4k=3\left(3h^{2}-k^{2}\right)\)yields 4k = 24, so k = 6. Substitute k=6 back to find \(h^{2}=44/3\)
Solving the given non-linear system requires direct substitution. By factoring the right side of the second equation as \(3\left(3h^{2}-k^{2}\right)\), we substitute the first equation's value (8) to get 4k = 24, meaning k = 6. Substituting k back into \(3h^{2}-k^{2}=8\) yields \(h^{2}=\frac{44}{3} ,\)making Option A correct over the originally provided key.
- Option B -> Represents 44/9, which incorrectly assumes \(h=\pm \frac{\sqrt{44}}{3}\) rather than \(h=\pm \sqrt{44/3}\)during evaluation.
- Option C -> Represents 8/3, which mathematically ignores the necessary \(k^{2}\) substitution completely.
- Option D -> Represents 16/9, which incorrectly evaluates the algebraic constants during isolation.
Used: Substitution
Application: Briefly applying substitution simplifies complex simultaneous equations by evaluating common algebraic groups, avoiding tedious quadratics.
Final Logic: Substituting the known value of \(3h^{2}-k^{2}\)directly isolates k, leading cleanly to the exact value for \(h^{2}\).
"Sub and Solve: Group the terms, find the root."
14
Use the evaluated coordinates \(h=\pm \sqrt{44/3}\) and k = 6. Substitute into the tangent format \(3hx-ky=8\) Simplifying the coefficients algebraically maps closest to intended Option A.
Using the endpoints derived previously \(h=\pm \sqrt{44/3}\) and k = 6, we apply the explicit tangent formula for the hyperbola: 3hx - ky = 8. Substituting these values gives \(\pm 2\sqrt{33}x-6y=8\). Dividing by 2 yields \(\pm \sqrt{33}x-3y=4\), aligning algebraically with the intended choice A despite formatting variances.
- Option B -> Uses \(\sqrt{11}\), completely missing the multiplication factor derived from the hyperbola's leading coefficient.
- Option C -> Reverses the y-coefficient sign improperly during the final algebraic transposition.
- Option D -> Omits the irrational coefficient \(\sqrt{33}\) entirely, failing to account for the true $h$ parameter value.
Used: Elimination
Application: By identifying the exact irrational coefficient \(\sqrt{33}\)and the correct proportional y-coefficient (-3), we immediately narrow the choices down and bypass extraneous solving.
Final Logic: The tangent structure 3hx - ky = 8 strictly mandates the \(\pm \sqrt{33}\) and -3 coefficients after simplification.
"Match the Math: h brings the root, k brings the slope."
15 In real-life change models involving geometric expansion, the rate of change of volume of a sphere strictly with respect to its surface area (dV/dS) evaluated exactly at a radius r = 5 m equates to:
V = 4/3 πr³ S = 4πr² Ratio simplifies to r/2
dV/dr = 4πr² dS/dr = 8πr So, dV/dS = (4πr²)/(8πr) = r/2 At r = 5: = 5/2 = 2.5
- Option A → ignores ratio form
- Option C → double value
- Option D → quarter value
Used: Dimensional/Unit Analysis
Application: The ratio of derivatives directly simplifies to a function of the radius, allowing for immediate and accurate numerical evaluation.
Final Logic: Ratio simplifies to r/2 → 2.5
"Surface grows twice → half rate"
16 In production and demand analysis, a firm establishes its linear price-demand relationship. If the firm sells 1400 units at ₹4 and 1800 units at ₹2, the derived linear price function p(x) strictly evaluates to:
Use two-point form Negative slope Solve intercept
Points: (1400,4), (1800,2) Slope = (2−4)/(1800−1400) = −1/200 So: p = mx + c 4 = −1400/200 + c = −7 + c → c = 11 Thus: p = 11 − x/200
- Option B → wrong slope sign
- Option C → incorrect model
- Option D → incorrect structure
Used: Elimination
Application: Applying the two-point linear model formula confirms the correct slope-intercept form, ensuring the demand function matches the data.
Final Logic: Only correct slope-intercept form fits data.
"Demand rises → price falls (− slope)"
17 Using tangent-based interpretation, find the explicit slope of the tangent to the curve y = (x^3 - 1)(x - 2) evaluated exactly at the point where it cuts the x-axis at (1,0).
Differentiate product Evaluate at x = 1 Substitute
y = (x³ − 1)(x − 2) y' = 3x²(x−2) + (x³−1) At x = 1: = 3(1)(−1) + 0 = −3
- Option A → incorrect evaluation
- Option B → ignores derivative value
- Option D → wrong sign
Used: Substitution
Application: Direct evaluation of the derivative at the given coordinate provides the slope, confirming the value without further complex steps.
Final Logic: Direct evaluation gives −3
"Plug 1 → only −3 survives"
18 In gradient applications, the implicit curve x^(2/3) + y^(2/3) = 2 features a tangent at the coordinate (1, 1). The corresponding equation of the normal line strictly evaluates to:
Implicit differentiation Slope = -1 Normal slope = 1
x^(2/3)+y^(2/3)=2 Differentiating: (2/3)x^(-1/3) + (2/3)y^(-1/3)y' = 0 y' = −1 at (1,1) Normal slope = 1 Equation: y − 1 = x − 1 → x − y = 0
- Option A → wrong intercept
- Option C → wrong slope sign
- Option D → incorrect form
Used: Contextual/Tonal Matching
Application: Deriving the tangent slope and applying the negative reciprocal rule for normals confirms the correct linear equation.
Final Logic: Normal line passes through (1,1) with slope 1
"Tangent −1 → Normal +1"
19 In derivative-based modelling, the Marginal Cost (MC) equation for a firm is explicitly derived from C(x) = x^2 + 30x + 1500. The exact numerical MC evaluated at a production level of 20 toys is:
MC = dC/dx Differentiate Substitute x = 20
C(x) = x² + 30x + 1500 MC = 2x + 30 At x = 20: = 40 + 30 = 70
- Option A → underestimation
- Option B → wrong substitution
- Option D → total cost, not marginal cost
Used: Substitution
Application: Differentiating the total cost function correctly isolates the marginal cost, allowing for simple substitution of the given production level.
Final Logic: Direct derivative evaluation gives 70
"2×20 + 30 = 70"
20 In applied mathematical problems involving higher-order polynomial curves, the specific curve y = 4x^3 - 2x^5 possesses tangents that strictly pass through the geometric origin (0,0). The valid x-coordinates of the points of contact are exactly:
Tangent condition at (a, f(a)) Passes through origin Solve equation
For y = 4x³ − 2x⁵, tangent at x = a passes through origin gives condition leading to: a(1 − a⁴) = 0 So: a = 0, ±1
- Option B → extra invalid roots
- Option C → unrelated values
- Option D → incorrect scaling
Used: Elimination
Application: Solving the tangent-origin pass-through condition confirms the only roots that satisfy the geometric requirement are 0 and ±1.
Final Logic: Only roots satisfying tangent-origin condition are 0, ±1
"Origin tangency → symmetric roots"
