UG Mathematics Booster Test 2 - Continuity Analysis & Functions
π Answers are locked once submitted β results and explanations appear at the end.
QUESTION 1 OF 20
f(x)=1/x
near x=0. As x approaches 0 from the right (e.g., 0.1, 0.01), the values of f(x)increase as 10, 100, β¦ . In symbols,
(limβ‘)β¬(xβ0^+ ) 1/x=+β
We emphasize that +βis not a real number, hence the limit does not exist as a real number.
Similarly, as xβ0^-,
(limβ‘)β¬(xβ0^- ) 1/x=-β
Thus, the function is discontinuous at x=0.
QUESTION 2 OF 20
f(x)=1/x
near x=0. As x approaches 0 from the right (e.g., 0.1, 0.01), the values of f(x)increase as 10, 100, β¦ . In symbols,
(limβ‘)β¬(xβ0^+ ) 1/x=+β
We emphasize that +βis not a real number, hence the limit does not exist as a real number.
Similarly, as xβ0^-,
(limβ‘)β¬(xβ0^- ) 1/x=-β
Thus, the function is discontinuous at x=0.
\(f(x)=\frac{1}{x}\)
Every rational function is continuous at all points except:
QUESTION 3 OF 20
Match the expressions with their values:
| List I | List II |
|---|---|
| 1. \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘5x}{x}\) | a. 2 |
| 2. \({limβ‘}_{x\rightarrow 0}\frac{\sin\,x}{3x}\) | b. -1 |
| 3. \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘(x+\pi )}{x}\) | c. 5 |
| 4. \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘2x}{x}\) | d. \(1/3\) |
QUESTION 4 OF 20
If \(f(x)\)and \(g(x)\)are continuous trigonometric functions, which of the following are continuous?
I. \(f(x)+g(x)\)
II. \(f(x)β
g(x)\)
III. \(\frac{f(x)}{g(x)}\), where \(g(x)\neq 0\)
QUESTION 5 OF 20
Identify the incorrect statement regarding
\(f(x)=\frac{1}{x}\)
QUESTION 6 OF 20
If a function is modeled by
\(f(t)=\frac{1}{t}\)
At what value of t does the function become undefined, causing an infinite spike?
QUESTION 7 OF 20
For the function
\(f(x)=\frac{1}{x}\)
consider the sequence \(x=\{0.1,0.01,0.001\}\). The corresponding values of \(f(x)\)are:
QUESTION 8 OF 20
For
\(f(x)=\frac{1}{x}\)
as x approaches 0 from the left, the values of the function:
QUESTION 9 OF 20
Let
\(f(x)=\left\{\begin{pmatrix}x+2, & x\leq 1\\ x-2, & x>1\end{pmatrix}\right.\)
A point is chosen uniformly at random from the interval [0,2].
What is the probability that the function is discontinuous at that point?
QUESTION 10 OF 20
Let
\(f(x)=\left\{\begin{pmatrix}x+2, & x<1\\ 3, & x=1\\ x-2, & x>1\end{pmatrix}\right.\)
The left-hand limit at x=1 is:
QUESTION 11 OF 20
Let
\(f(x)=β£xβ£\)
Is the function continuous for all negative real numbers \(x<0\)?
QUESTION 12 OF 20
While evaluating
\(\int β£xβ£βdx\)
we split the domain at x=0 because:
QUESTION 13 OF 20
Assertion (A): For an integer n and sufficiently small \(r>0\),
\([n-r]=n-1,[n+r]=n\)
Reason (R): The function \(f(x)=[x]\)is continuous at every integer.
QUESTION 14 OF 20
Arrange the steps for evaluating the right-hand limit of \(\left[x\right]\)at an integer n:
1. Substitute \(x=n+r\)
2. Set the limit \(x\rightarrow n^{+}\)
3. Evaluate \(\left[n,\ r\right]\)
4. Result is n
QUESTION 15 OF 20
If
\(f(x)=sinβ‘x,g(x)=x^{2}\)
then the composition \(\left(f\circ g)(x\right)\)is:
QUESTION 16 OF 20
Suppose f and g are real-valued functions. The composite function \(f\circ g\) is continuous at \(x=c\) provided:
QUESTION 17 OF 20
The identity function
\(f(x)=x\)
is:
QUESTION 18 OF 20
For a function defined on a closed interval [a,b], continuity requires:
QUESTION 19 OF 20
Let
\(f(x)=\left\{\begin{pmatrix}x^{2}, & x\leq 1\\ x^{2}, & x>1\end{pmatrix}\right.\)
The graph has how many breaks?
QUESTION 20 OF 20
A function has
\(LHL=3,RHL=-1\)
at \(x=a\). The graph at \(x=a\) shows:
Test Complete!
Answer Review
1
f(x)=1/x
near x=0. As x approaches 0 from the right (e.g., 0.1, 0.01), the values of f(x)increase as 10, 100, β¦ . In symbols,
(limβ‘)β¬(xβ0^+ ) 1/x=+β
We emphasize that +βis not a real number, hence the limit does not exist as a real number.
Similarly, as xβ0^-,
(limβ‘)β¬(xβ0^- ) 1/x=-β
Thus, the function is discontinuous at x=0.
Polynomials have no denominator restrictions Polynomial graphs are unbroken Continuous for all real x
Unlike the reciprocal function \(\frac{1}{x}\), polynomial functions are continuous for every real number. They do not have infinite limits or undefined points caused by zero denominators. Hence option B is correct. Polynomial graphs remain smooth and connected without breaks across the real line.
- Option A β Infinite limits arise in reciprocal-type functions, not polynomials.
- Option C β Polynomials are continuous at x=0 and everywhere else.
- Option D β Polynomial graphs do not contain breaks or jumps.
Used: Odd One Out
Application:
- Compare reciprocal discontinuity with polynomial continuity.
Final Logic:
- Polynomials remain continuous everywhere on β.
"Polynomial = No breaks"
2
f(x)=1/x
near x=0. As x approaches 0 from the right (e.g., 0.1, 0.01), the values of f(x)increase as 10, 100, β¦ . In symbols,
(limβ‘)β¬(xβ0^+ ) 1/x=+β
We emphasize that +βis not a real number, hence the limit does not exist as a real number.
Similarly, as xβ0^-,
(limβ‘)β¬(xβ0^- ) 1/x=-β
Thus, the function is discontinuous at x=0.
\(f(x)=\frac{1}{x}\)
Every rational function is continuous at all points except:
Rational functions fail at denominator zero Else continuity is preserved Undefined points create discontinuities
A rational function is continuous wherever it is defined. Discontinuities occur only where the denominator becomes zero because division by zero is undefined. Hence option D is correct. The function \(\frac{1}{x}\)fails specifically at x=0 for this reason.
- Option A β Integers do not automatically create discontinuity.
- Option B β Rational numbers can belong to the continuity domain.
- Option C β Irrational numbers do not inherently cause discontinuity.
Used: Elimination
Application:
- Identify the only mathematically valid discontinuity condition.
Final Logic:
- Rational functions break only at denominator zeros.
"Denominator 0 β Discontinuity"
3 Match the expressions with their values:
| List I | List II |
|---|---|
| 1. \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘5x}{x}\) | a. 2 |
| 2. \({limβ‘}_{x\rightarrow 0}\frac{\sin\,x}{3x}\) | b. -1 |
| 3. \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘(x+\pi )}{x}\) | c. 5 |
| 4. \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘2x}{x}\) | d. \(1/3\) |
Use standard \(limβ‘\frac{\sin\,x}{x}=1\) Factor constants carefully Apply trigonometric identities
Using: \({limβ‘}_{x\rightarrow 0}\frac{\sin\,x}{x}=1{limβ‘}_{x\rightarrow 0}\frac{sinβ‘5x}{x}=5{limβ‘}_{x\rightarrow 0}\frac{\sin\,x}{3x}=\frac{1}{3}\) Since: \(sinβ‘(x+\pi )=-sinβ‘x\) the third limit becomes β1. Also: \({limβ‘}_{x\rightarrow 0}\frac{sinβ‘2x}{x}=2\) Hence option A is correct.
- Option B β Incorrectly matches limits involving constants and signs.
- Option C β Misuses standard trigonometric limit values.
- Option D β Incorrect mapping for second and fourth expressions.
Used: Substitution
Application:
- Reduce every expression to the standard sine limit form.
Final Logic:
- Apply \(limβ‘\frac{\sin\,x}{x}=1\) systematically.
"sin(kx)/x β k"
4 If \(f(x)\)and \(g(x)\)are continuous trigonometric functions, which of the following are continuous?
I. \(f(x)+g(x)\)
II. \(f(x)β
g(x)\)
III. \(\frac{f(x)}{g(x)}\), where \(g(x)\neq 0\)
Continuous functions preserve operations Sum and product remain continuous Quotient continuous if denominator nonzero
NCERT states that sums, products, and quotients of continuous functions remain continuous wherever defined. Therefore: \(f+g,fg,\frac{f}{g}\) are continuous provided \(g(x)\neq 0\). Hence all three statements are correct, making option A the correct answer.
- Option B β Ignores quotient continuity condition.
- Option C β Sum of continuous functions is also continuous.
- Option D β Product and quotient continuity are also valid results.
Used: Option Grouping
Application:
- Apply algebra of continuous functions.
Final Logic:
- Sum, product, and quotient preserve continuity.
"Add, multiply, divide (β 0) β Continuous"
5 Identify the incorrect statement regarding
\(f(x)=\frac{1}{x}\)
Infinity is not a real number Reciprocal limits become unbounded Hence ordinary limit does not exist
For: \(f(x)=\frac{1}{x}\) the left-hand limit is \(-\infty\) and the right-hand limit is \(+\infty\). However, infinity is not a real number, so the two-sided real limit does not exist. Hence option C is the incorrect statement.
- Option A β Correct description of left-hand behavior near zero.
- Option B β Correct description of right-hand behavior near zero.
- Option D β The limit does not exist as a finite real number.
Used: Extreme Word Filter
Application:
- Check conceptual correctness of "infinity as real number."
Final Logic:
- Infinity represents unbounded growth, not a real number.
"β is not real"
6 If a function is modeled by
\(f(t)=\frac{1}{t}\)
At what value of t does the function become undefined, causing an infinite spike?
Denominator zero causes undefined value Reciprocal spikes near zero Infinite discontinuity occurs at t=0
The reciprocal function: \(f(t)=\frac{1}{t}\) is undefined when the denominator equals zero. Therefore at: \(t=0\) the graph shows an infinite spike or vertical asymptote. Hence option D is correct.
- Option A β \(\frac{1}{1}\)is finite and defined.
- Option B β \(\frac{1}{-1}\)exists and equals β1.
- Option C β \(\frac{1}{2}\)is finite and continuous.
Used: Substitution
Application:
- Identify where denominator becomes zero.
Final Logic:
- Reciprocal functions fail at zero denominator.
"1/t explodes at 0"
7 For the function
\(f(x)=\frac{1}{x}\)
consider the sequence \(x=\{0.1,0.01,0.001\}\). The corresponding values of \(f(x)\)are:
Positive small numbers give large reciprocals Values increase rapidly near zero Sequence grows unbounded positively
For: \(x=0.1,0.01,0.001\) the reciprocal values are: \(10,100,1000\) which grow rapidly without bound. Hence the sequence approaches large positive values as x approaches zero from the positive side. Therefore option C is correct.
- Option A β Values move away from zero, not toward it.
- Option B β Values remain positive, not negative.
- Option D β Reciprocal values clearly change and increase.
Used: Substitution
Application:
- Directly compute reciprocal values of the sequence.
Final Logic:
- Smaller positive denominators create larger positive reciprocals.
"Tiny positive β Huge positive"
8 For
\(f(x)=\frac{1}{x}\)
as x approaches 0 from the left, the values of the function:
Left-side values remain negative Reciprocal magnitude grows infinitely Values decrease beyond all bounds
As x approaches 0 from the negative side, x becomes a very small negative number. Therefore: \(\frac{1}{x}\rightarrow -\infty\) meaning the function becomes smaller than every negative real number. Hence option B is correct.
- Option A β Positive infinity occurs only from the right side.
- Option C β Reciprocal values become unbounded, not zero.
- Option D β Values do not oscillate around 1.
Used: Substitution
Application:
- Use small negative numbers near zero.
Final Logic:
- Negative tiny denominators produce large negative reciprocals.
"Left of 0 β ββ"
9 Let
\(f(x)=\left\{\begin{pmatrix}x+2, & x\leq 1\\ x-2, & x>1\end{pmatrix}\right.\)
A point is chosen uniformly at random from the interval [0,2].
What is the probability that the function is discontinuous at that point?
Function discontinuous only at one point Single points have zero probability Continuous almost everywhere on interval
The function is discontinuous only at: \(x=1\) In a continuous interval, the probability of selecting one exact point is zero. Therefore: \(P(discontinuity)=0\) Hence option A is correct. The provided answer B is incorrect.
- Option B β A single point cannot occupy half the interval probability.
- Option C β The function is continuous at all other points.
- Option D β Uniform probability on intervals is properly defined.
Used: Dimensional/Unit Analysis
Application:
- Compare point length with total interval length.
Final Logic:
- Single points have zero geometric probability.
"One point β Probability 0"
10 Let
\(f(x)=\left\{\begin{pmatrix}x+2, & x<1\\ 3, & x=1\\ x-2, & x>1\end{pmatrix}\right.\)
The left-hand limit at x=1 is:
Use expression valid for x<1 Substitute x=1 in x+2 Left-hand limit equals 3
For the left-hand limit, use the branch: \(f(x)=x+2,x<1\) Therefore: \({limβ‘}_{x\rightarrow 1^{-}}f(x)=1+2=3\) Hence option A is correct. The actual value at x=1 does not affect the left-hand limit.
- Option B β Incorrect substitution result.
- Option C β Comes from the right-side branch \(x-2\).
- Option D β No valid branch evaluation gives zero.
Used: Substitution
Application:
- Use the left-side branch for LHL evaluation.
Final Logic:
- Left-hand limits depend only on nearby left-side values.
"LHL uses left branch"
11 Let
\(f(x)=β£xβ£\)
Is the function continuous for all negative real numbers \(x<0\)?
For negative x, \(β£xβ£=-x\) Linear functions are continuous Limit equals function value everywhere
For \(x<0\), \(β£xβ£=-x\) which is a linear polynomial function and therefore continuous. If \(c<0\), \({limβ‘}_{x\rightarrow c}β£xβ£=-c=f(c)\) Hence the modulus function is continuous for all negative real numbers. Therefore option D is correct.
- Option A β \(β£xβ£=-x\) is true, but this does not imply discontinuity.
- Option B β For negative x, \(β£xβ£\neq x\).
- Option C β The limit equals \(-c\), not c, for negative values.
Used: Substitution
Application:
- Replace \(β£xβ£\)by \(-x\) for negative inputs.
Final Logic:
- Linear expressions remain continuous everywhere.
"Negative x β |x| = βx"
12 While evaluating
\(\int β£xβ£βdx\)
we split the domain at x=0 because:
Modulus has piecewise definition Formula changes at x=0 Integration requires separate expressions
The modulus function satisfies: \(β£xβ£=\left\{\begin{pmatrix}-x, & x<0\\ x, & x\geq 0\end{pmatrix}\right.\) Since its algebraic form changes at x=0, the integral must be evaluated separately on each interval. Hence option C is correct. The function remains continuous and finite at x=0.
- Option A β The limit exists and equals zero at x=0.
- Option B β The modulus function is defined at x=0.
- Option D β The integral of \(β£xβ£\)remains finite over bounded intervals.
Used: Contextual/Tonal Matching
Application:
- Use the piecewise definition of modulus.
Final Logic:
- Change in algebraic expression requires interval splitting.
"|x| splits at 0"
13 Assertion (A): For an integer n and sufficiently small \(r>0\),
\([n-r]=n-1,[n+r]=n\)
Reason (R): The function \(f(x)=[x]\)is continuous at every integer.
Greatest integer jumps at integers One-sided values differ there Hence continuity fails at integers
For sufficiently small positive r, \([n-r]=n-1\) and \([n+r]=n\) Thus the Assertion is true. However, the greatest integer function has jump discontinuities at every integer, so it is not continuous there. Therefore the Reason is false. Hence option B is correct.
- Option A β Assertion is mathematically correct.
- Option C β The Reason is false and cannot explain the Assertion.
- Option D β The Assertion correctly describes one-sided behavior near integers.
Used: Substitution
Application:
- Evaluate nearby left and right values around integer n.
Final Logic:
- Unequal neighboring values create discontinuity at integers.
"GIF jumps at integers"
14 Arrange the steps for evaluating the right-hand limit of \(\left[x\right]\)at an integer n:
1. Substitute \(x=n+r\)
2. Set the limit \(x\rightarrow n^{+}\)
3. Evaluate \(\left[n,\ r\right]\)
4. Result is n
Start with right-hand approach Substitute nearby positive increment Evaluate greatest integer value
To evaluate the right-hand limit: First consider: \(x\rightarrow n^{+}\) Then write: \(x=n+r,r>0\) Next evaluate: \([n+r]=n\) Thus the final result is n. Therefore the correct order is: \(2,1,3,4\) Hence option D is correct. The provided answer is correct.
- Option A β Substitution occurs after specifying right-hand approach.
- Option B β Logical evaluation order is reversed completely.
- Option C β Evaluation cannot occur before substitution.
Used: Contextual/Tonal Matching
Application:
- Follow the natural procedural order of limit evaluation.
Final Logic:
- Right-hand approach precedes substitution and evaluation.
"Approach β Substitute β Evaluate β Result"
15 If
\(f(x)=sinβ‘x,g(x)=x^{2}\)
then the composition \(\left(f\circ g)(x\right)\)is:
Composition means outer after inner First compute \(g(x)\) Then apply sine function
By definition: \(\left(f\circ g)(x)=f(g(x)\right)\) Since: \(g(x)=x^{2}\) we get: \(f(g(x))=sinβ‘(x^{2})\) Hence option A is correct. The other options represent multiplication or different expressions, not composition.
- Option B β Represents product, not composition.
- Option C β Ambiguous notation lacking proper brackets.
- Option D β Squares the sine function instead of the input variable.
Used: Substitution
Application:
- Substitute the inner function into the outer function.
Final Logic:
- Composition means "function inside function."
"Compose = Put inside"
16 Suppose f and g are real-valued functions. The composite function \(f\circ g\) is continuous at \(x=c\) provided:
Inner function must behave continuously Outer function continuous at image point Composite continuity follows sequentially
For: \(\left(f\circ g)(x)=f(g(x)\right)\) continuity requires: 1. \(g\) continuous at c 2. \(f\) continuous at \(g(c)\) Then: \(f(g(x))\rightarrow f(g(c))\) Hence option C is correct. Continuity of only one function is insufficient.
- Option A β Ignores continuity of the inner function g.
- Option B β A discontinuous inner function may destroy composite continuity.
- Option D β Composite continuity always requires conditions on f and g.
Used: Option Grouping
Application:
- Identify continuity requirements for both inner and outer functions.
Final Logic:
- Both linked continuity conditions are necessary.
"Inner continuous, outer continuous"
17 The identity function
\(f(x)=x\)
is:
Identity returns input unchanged Limit equals function value directly Continuous throughout real numbers
For the identity function: \(f(x)=x\) we have: \({limβ‘}_{x\rightarrow a}x=a=f(a)\) for every real number a. Thus the function is continuous everywhere on β. Hence option B is correct according to the continuity definition.
- Option A β Identity function remains continuous at x=0 also.
- Option C β The domain includes all real numbers.
- Option D β Identity functions are polynomial functions, not only rational functions.
Used: Substitution
Application:
- Directly evaluate the limit at an arbitrary point.
Final Logic:
- Limit equals function value for every real input.
"Identity stays continuous"
18 For a function defined on a closed interval [a,b], continuity requires:
Closed intervals include endpoints Endpoint continuity uses one-sided limits Interior continuity also required
A function is continuous on a closed interval [a,b] if: β’ It is continuous for all interior points β’ Right-hand continuity exists at a β’ Left-hand continuity exists at b Thus continuity must hold at every point including endpoints. Hence option A is correct.
- Option B β Endpoint continuity is also necessary on closed intervals.
- Option C β Endpoints may still satisfy continuity conditions.
- Option D β Endpoint values need not be zero.
Used: Contextual/Tonal Matching
Application:
- Apply the formal definition of continuity on closed intervals.
Final Logic:
- Endpoints and interior points all matter.
"Closed interval β Include endpoints"
19 Let
\(f(x)=\left\{\begin{pmatrix}x^{2}, & x\leq 1\\ x^{2}, & x>1\end{pmatrix}\right.\)
The graph has how many breaks?
Both branches are identical Polynomial function remains continuous No jumps or holes occur
Both branches define the same function: \(f(x)=x^{2}\) which is continuous everywhere. Since there is no change in expression or limiting behavior at x=1, the graph has no breaks. Hence option D is correct.
- Option A β No discontinuity exists to create two breaks.
- Option B β Polynomial graphs remain connected and smooth.
- Option C β No jump or removable discontinuity occurs at x=1.
Used: Odd One Out
Application:
- Observe that both branches are actually identical.
Final Logic:
- Same expressions on both sides preserve continuity.
"Same branch = No break"
20 A function has
\(LHL=3,RHL=-1\)
at \(x=a\). The graph at \(x=a\) shows:
One-sided limits are unequal Overall limit does not exist Jump discontinuity appears graphically
Since: \(LHL\neq RHL\) the limit at x=a does not exist. Therefore the graph contains a jump discontinuity or visible break at that point. Hence option C is correct. A smooth or connected graph requires equal one-sided limits.
- Option A β Smooth curves require equal left and right limits.
- Option B β Sharp corners still preserve continuity.
- Option D β Vertical asymptotes involve unbounded behavior, not finite unequal limits.
Used: Elimination
Application:
- Remove continuous graph possibilities when one-sided limits differ.
Final Logic:
- Unequal LHL and RHL imply graphical break.
"Unequal limits β Gap"
