CUET UG Mathematics Booster Test 1 - Variable Separable Method
π Answers are locked once submitted β results and explanations appear at the end.
QUESTION 1 OF 20
Express the differential equation
\(x(x^{2}+1)\frac{dy}{dx}=y\)
in its cleanly separated variable form.
QUESTION 2 OF 20
Identify the INCORRECT statement regarding the equation
\(\frac{dy}{dx}=sinβ‘(x+y).\)
QUESTION 3 OF 20
Arrange the correct sequence of steps to solve \(\frac{dy}{dx}=(x+1)(2-y).\)
QUESTION 4 OF 20
Match the differential equations with their correct isolated terms.
| List I | List II |
|---|---|
| 1. \(y^{'}=e^{x}e^{-y}\) | a. \(e^{y}βdy=e^{x}βdx\) |
| 2. \(y^{'}=\frac{x^{2}}{y^{2}}\) | b. \(y^{2}βdy=x^{2}βdx\) |
| 3. \(y^{'}=xy\) | c. \(\frac{dy}{y}=xβdx\) |
| 4. \(y^{'}=\frac{x}{y}\) | d. \(yβdy=xβdx\) |
QUESTION 5 OF 20
Evaluate the general solution resulting from \(\int yβdy=\int x^{2}βdx.\)
QUESTION 6 OF 20
Consider \(\frac{dy}{dx}=\frac{1}{x}.\)
Which expressions correctly incorporate the arbitrary constant?
QUESTION 7 OF 20
Assertion (A): The solution of \(\frac{dy}{dx}=-\frac{x}{y}\)is \(x^{2}+y^{2}=C\).
Reason (R): \(yβdy=-xβdx\) integrates to \(x^{2}+y^{2}=C_{1}\), forming concentric circles.
QUESTION 8 OF 20
The general solution \(y=Cx\)
corresponding to \(\frac{dy}{dx}=\frac{y}{x}\)
represents which region?
QUESTION 9 OF 20
If the velocity components satisfy \(\frac{dy}{dx}=-\frac{y}{x},\)
what is the equation of the trajectory?
QUESTION 10 OF 20
Find the geometric area enclosed by the coordinate axes and the curve satisfying \(\frac{dy}{dx}=-1\) which passes through \(\left(4\ ,\ 0\right)\).
QUESTION 11 OF 20
Solve the equation \(\frac{dy}{dx}=\frac{1}{1+x^{2}}\)
given the initial condition \(y(0)=\pi /4\).
QUESTION 12 OF 20
A probabilistic survival variable follows the path \(\frac{dp}{dt}=pcosβ‘t.\)
Find \(p(t)\)exactly if \(p(0)=1\).
QUESTION 13 OF 20
Solve \(\frac{dy}{dx}=e^{3x}\)
subjected to the initial parameter \(y(0)=1/3\). Compute the value of \(y(1)\).
QUESTION 14 OF 20
A continuous moving average dataset exhibits a precise rate of change modeled by \(\frac{dy}{dx}=2x.\)
If the data point \(\left(1\ ,\ 4\right)\)is recorded, what is the evaluated integration constant \(C\)?
QUESTION 15 OF 20
A curve passes through \(\left(-2,3\right)\)and possesses the slope \(\frac{2x}{y^{2}}\)
at any point \(\left(x\ ,\ y\right)\). Calculate the exact value of \(y\) when \(x=2\).
QUESTION 16 OF 20
The variable separable differential equation \(\frac{dy}{dx}=-\frac{x}{y}\)
defines which orthogonal family related to the linear equations \(y=kx\)?
QUESTION 17 OF 20
If a restricted population grows according to \(\frac{dP}{dt}=0.1P\)
and \(P(0)=1000\), calculate the approximate population at \(t=10\)(use \(e\approx 2.718\)).
QUESTION 18 OF 20
If βΉ100 doubles in 10 years under continuous compounding, which expression solves for the rate \(r\%\)?
QUESTION 19 OF 20
\(4\pi r^{2}dr=kdt,\)
separating variables and integrating yields a relationship primarily between:
QUESTION 20 OF 20
Test Complete!
Answer Review
1 Express the differential equation
\(x(x^{2}+1)\frac{dy}{dx}=y\)
in its cleanly separated variable form.
Move \(y\) to the left side. Move \(dx\) to the right side. Separate variables completely.
Starting from \(x(x^{2}+1)\frac{dy}{dx}=y,\) divide by \(y\) and multiply by \(dx\): \(\frac{dy}{y}=\frac{dx}{x(x^{2}+1)}.\) This places all \(y\)-terms on one side and all \(x\)-terms on the other, satisfying the condition for variable separation. Hence Option B is correct.
- Option A β Does not follow from algebraic rearrangement of the given equation.
- Option C β Incorrect separation; \(y\) should appear in the denominator.
- Option D β Omits the factor \(\left(x^{2}\ +\ 1\right)\), so it is not equivalent.
Used: Elimination
Application:
- Rearrange the equation and eliminate options that do not isolate \(x\) and \(y\).
Final Logic:
- Separated form must contain only \(y\)-terms on one side and \(x\)-terms on the other.
"Separate β y left, x right."
2 Identify the INCORRECT statement regarding the equation
\(\frac{dy}{dx}=sinβ‘(x+y).\)
RHS contains \(x+y\). Not factorizable into \(g(x)h(y)\). Direct separation fails.
A separable equation requires \(\frac{dy}{dx}=g(x)h(y).\) The expression \(sinβ‘(x+y)\)depends on the combination \(x+y\), not on separate functions of \(x\) and \(y\). Therefore it is not directly separable. Hence Option C is the incorrect statement.
- Option A β Correct because direct separation is impossible.
- Option B β Correct since \(sinβ‘(x+y)\)is not a product \(g(x)h(y)\).
- Option D β Correct; substitution \(v=x+y\) is a standard approach.
Used: Odd One Out
Application:
- Identify the statement contradicting the definition of separable equations.
Final Logic:
- Only Option C incorrectly labels the equation as directly separable.
"x+y together β not separable."
3 Arrange the correct sequence of steps to solve \(\frac{dy}{dx}=(x+1)(2-y).\)
Start with given DE. Separate variables. Integrate both sides. Write final solution.
The logical sequence is: 1. Write the DE. 2. Separate variables. 3. Integrate both sides. 4. Obtain the final relation. Thus: \(4\rightarrow 3\rightarrow 2\rightarrow 1.\) Hence Option D is correct.
- Option A β Integrates before separation.
- Option B β Starts from an intermediate step.
- Option C β Incorrect ordering of integration and separation.
Used: Contextual/Tonal Matching
Application:
- Follow the standard NCERT solution process.
Final Logic:
- DE β Separation β Integration β Solution.
"Given β Separate β Integrate β Solve."
4 Match the differential equations with their correct isolated terms.
| List I | List II |
|---|---|
| 1. \(y^{'}=e^{x}e^{-y}\) | a. \(e^{y}βdy=e^{x}βdx\) |
| 2. \(y^{'}=\frac{x^{2}}{y^{2}}\) | b. \(y^{2}βdy=x^{2}βdx\) |
| 3. \(y^{'}=xy\) | c. \(\frac{dy}{y}=xβdx\) |
| 4. \(y^{'}=\frac{x}{y}\) | d. \(yβdy=xβdx\) |
Rearrange each equation. Separate variables. Match corresponding forms.
Separating: 1 β \(e^{y}dy=e^{x}dx\)β a 2 β \(y^{2}dy=x^{2}dx\)β b 3 β \(\frac{dy}{y}=xdx\)β c 4 β \(ydy=xdx\)β d Hence Option A is correct.
- Option B β Incorrectly swaps equations 1 and 2.
- Option C β Misplaces equations 2 and 3.
- Option D β Several mismatches occur.
Used: Option Grouping
Application:
- Solve each correspondence independently.
Final Logic:
- Each equation has a unique separated form.
"Separate first, match later."
5 Evaluate the general solution resulting from \(\int yβdy=\int x^{2}βdx.\)
Integrate both sides directly. Use standard formulas. Add integration constant.
\(\int yβdy=\frac{y^{2}}{2}\) and \(\int x^{2}dx=\frac{x^{3}}{3}+C.\) Therefore, \(\frac{y^{2}}{2}=\frac{x^{3}}{3}+C.\) Hence Option B is correct.
- Option A β Incorrect integration of \(yβdy\).
- Option C β Missing factor \(1/2\).
- Option D β Not obtained from the given integrals.
Used: Substitution
Application:
- Apply standard integration formulas.
Final Logic:
- \(\int ydy=y^{2}/2\).
"Power rule on both sides."
6 Consider \(\frac{dy}{dx}=\frac{1}{x}.\)
Which expressions correctly incorporate the arbitrary constant?
Integrate \(1/x\). Constants can be absorbed. Compare equivalent forms.
Integration gives \(y=lnβ‘β£xβ£+C.\) Also, \(y=lnβ‘β£Cxβ£\) is equivalent because \(lnβ‘β£Cxβ£=lnβ‘β£xβ£+lnβ‘β£Cβ£.\) Statement 3 is not equivalent. Hence Option C is correct.
- Option A β Ignores another valid form.
- Option B β Statement 3 is incorrect.
- Option D β Includes an invalid expression.
Used: Option Grouping
Application:
- Check equivalence of logarithmic forms.
Final Logic:
- Statements 1 and 2 represent the same solution family.
"Log constant can move inside."
7 Assertion (A): The solution of \(\frac{dy}{dx}=-\frac{x}{y}\)is \(x^{2}+y^{2}=C\).
Reason (R): \(yβdy=-xβdx\) integrates to \(x^{2}+y^{2}=C_{1}\), forming concentric circles.
Separate variables. Integrate. Obtain circle family.
\(yβdy=-xβdx.\) Integrating: \(\frac{y^{2}}{2}=-\frac{x^{2}}{2}+C.\) Rearranging: \(x^{2}+y^{2}=C_{1}.\) The solution represents concentric circles. Thus both Assertion and Reason are true, and the Reason explains the Assertion.
- Option A β Both statements are correct.
- Option B β Reason is not false.
- Option C β Assertion is also true.
Used: Substitution
Application:
- Directly solve the differential equation.
Final Logic:
- Integration produces \(x^{2}+y^{2}=C\).
"βx/y β circles."
8 The general solution \(y=Cx\)
corresponding to \(\frac{dy}{dx}=\frac{y}{x}\)
represents which region?
Solution is \(y=Cx\). Slope varies with \(C\). All lines pass through origin.
The solution family \(y=Cx\) represents straight lines with different slopes. Every member passes through the origin. Hence Option A correctly describes the geometric family.
- Option B β Horizontal lines have form \(y=C\).
- Option C β Circles require quadratic terms.
- Option D β Parabolas require degree-two expressions.
Used: Contextual/Tonal Matching
Application:
- Recognize the graph of \(y=Cx\).
Final Logic:
- Straight-line family through origin.
"y = Cx β line family."
9 If the velocity components satisfy \(\frac{dy}{dx}=-\frac{y}{x},\)
what is the equation of the trajectory?
Separate variables. Integrate logarithms. Simplify solution.
\(\frac{dy}{y}=-\frac{dx}{x}.\) Integrating: \(lnβ‘β£yβ£=-lnβ‘β£xβ£+C.\) Therefore \(lnβ‘β£xyβ£=C\) or \(xy=C_{1}.\) Hence Option B is correct.
- Option A β Not obtained from integration.
- Option C β Corresponds to \(\frac{dy}{dx}=\frac{y}{x}\).
- Option D β Represents circle family.
Used: Substitution
Application:
- Use separation of variables.
Final Logic:
- \(lnβ‘β£xyβ£=C\Rightarrow xy=C\).
"dy/y = βdx/x β xy = constant."
10 Find the geometric area enclosed by the coordinate axes and the curve satisfying \(\frac{dy}{dx}=-1\) which passes through \(\left(4\ ,\ 0\right)\).
Integrate differential equation. Determine line equation. Compute triangular area.
\(\frac{dy}{dx}=-1\) gives \(y=-x+C.\) Using \(\left(4\ ,\ 0\right)\), \(C=4.\) Thus \(y=-x+4.\) The intercepts are 4 and 4. Area enclosed with axes: \(\frac{1}{2}(4)(4)=8.\) Hence Option C is correct.
- Option A β Area calculation is too small.
- Option B β Equals rectangle area, not triangle area.
- Option D β Incorrect geometric computation.
Used: Substitution
Application:
- Find the particular line, then apply area formula.
Final Logic:
- Area \(=\frac{1}{2}\times 4\times 4=8\).
"Intercept triangle β Β½ Γ base Γ height."
11 Solve the equation \(\frac{dy}{dx}=\frac{1}{1+x^{2}}\)
given the initial condition \(y(0)=\pi /4\).
Integrate the differential equation. Apply the initial condition. Determine the constant.
Integrating, \(y=\int \frac{dx}{1+x^{2}}={tanβ‘}^{-1}x+C.\) Using \(y(0)=\pi /4\), \(\pi /4={tanβ‘}^{-1}(0)+C=C.\) Thus \(y={tanβ‘}^{-1}x+\frac{\pi }{4}.\) Hence Option D is correct. Options A and B use incorrect constants, while C uses the wrong antiderivative.
- Option A β Does not satisfy \(y(0)=\pi /4\).
- Option B β Gives \(y(0)=-\pi /4\).
- Option C β Integral of \(\frac{1}{1+x^{2}}\)is not \({sinβ‘}^{-1}x\).
Used: Substitution
Application:
- Integrate and use the initial value immediately.
Final Logic:
- \(C=\pi /4\).
"1+xΒ² β tanβ»ΒΉx."
12 A probabilistic survival variable follows the path \(\frac{dp}{dt}=pcosβ‘t.\)
Find \(p(t)\)exactly if \(p(0)=1\).
Separate variables. Integrate both sides. Apply initial condition.
\(\frac{dp}{p}=cosβ‘tβdt.\) Integrating, \(lnβ‘p=sinβ‘t+C.\) Thus \(p=Ce^{\sin\,t}.\) Using \(p(0)=1\), \(1=Ce^{0},\) so \(C=1\). Hence \(p=e^{\sin\,t}.\) Option A is correct.
- Option B β Differentiation does not satisfy the equation.
- Option C β Not obtained from exponential growth form.
- Option D β Does not satisfy \(p^{'}=pcosβ‘t\).
Used: Substitution
Application:
- Convert to separable form and integrate.
Final Logic:
- \(lnβ‘p=sinβ‘t+C\).
"pβ²=pf(t) β p=e^{\int f(t)dt}."
13 Solve \(\frac{dy}{dx}=e^{3x}\)
subjected to the initial parameter \(y(0)=1/3\). Compute the value of \(y(1)\).
Integrate exponential function. Use initial condition. Evaluate at x=1.
\(y=\int e^{3x}dx=\frac{e^{3x}}{3}+C.\) Using \(y(0)=1/3\), \(\frac{1}{3}=\frac{1}{3}+C,\) so \(C=0\). Therefore \(y(1)=\frac{e^{3}}{3}.\) Hence Option B is correct.
- Option A β Missing factor \(1/3\).
- Option C β Adds an unnecessary constant.
- Option D β Multiplies instead of divides.
Used: Substitution
Application:
- Integrate and apply the given condition.
Final Logic:
- \(C=0\Rightarrow y(1)=e^{3}/3\).
"β«e^(ax)dx = e^(ax)/a."
14 A continuous moving average dataset exhibits a precise rate of change modeled by \(\frac{dy}{dx}=2x.\)
If the data point \(\left(1\ ,\ 4\right)\)is recorded, what is the evaluated integration constant \(C\)?
Integrate derivative. Substitute given point. Solve for C.
Integrating, \(y=x^{2}+C.\) Using the point \(\left(1\ ,\ 4\right)\), \(4=1+C.\) Hence \(C=3.\) Therefore Option C is correct.
- Option A β Does not satisfy the point.
- Option B β Gives y=3 at x=1.
- Option D β Gives y=5 at x=1.
Used: Substitution
Application:
- Insert the known point into the general solution.
Final Logic:
- \(4=1+C\).
"Point determines C."
15 A curve passes through \(\left(-2,3\right)\)and possesses the slope \(\frac{2x}{y^{2}}\)
at any point \(\left(x\ ,\ y\right)\). Calculate the exact value of \(y\) when \(x=2\).
Separate variables. Form particular curve. Evaluate at x=2.
\(y^{2}dy=2xβdx.\) Integrating, \(\frac{y^{3}}{3}=x^{2}+C.\) Using \(\left(-2,3\right)\), \(9=4+C,\) so \(C=5\). Thus \(y^{3}=3x^{2}+15.\) At \(x=2\), \(y^{3}=27,\) giving \(y=3\).
- Option A β Does not satisfy the equation.
- Option B β Gives \(y^{3}=-27\), inconsistent with the curve.
- Option C β Gives \(y^{3}=8\), incorrect.
Used: Substitution
Application:
- Determine the particular curve first.
Final Logic:
- \(y^{3}=27\Rightarrow y=3\).
"Find C before evaluating."
16 The variable separable differential equation \(\frac{dy}{dx}=-\frac{x}{y}\)
defines which orthogonal family related to the linear equations \(y=kx\)?
Separate variables. Integrate. Identify geometric family.
Integrating, \(ydy=-xdx,\) gives \(x^{2}+y^{2}=C.\) This is the family of circles centered at the origin. These circles are orthogonal to radial lines \(y=kx\). Hence Option A is correct.
- Option B β Hyperbolas arise from differences of squares.
- Option C β Parabolas require quadratic-variable relations.
- Option D β Ellipses have unequal coefficients.
Used: Substitution
Application:
- Solve the DE and recognize the curve family.
Final Logic:
- \(x^{2}+y^{2}=C\).
"βx/y β circle family."
17 If a restricted population grows according to \(\frac{dP}{dt}=0.1P\)
and \(P(0)=1000\), calculate the approximate population at \(t=10\)(use \(e\approx 2.718\)).
Use exponential growth model. Substitute t=10. Approximate using e.
The solution is \(P=1000e^{0.1t}.\) At \(t=10\), \(P=1000e.\) Using \(e\approx 2.718\), \(P\approx 2718.\) Hence Option B is correct.
- Option A β Ignores growth.
- Option C β Underestimates the exponential increase.
- Option D β Not the calculated value.
Used: Substitution
Application:
- Apply the growth formula directly.
Final Logic:
- \(P(10)=1000e\).
"Growth β multiply by e^(kt)."
18 If βΉ100 doubles in 10 years under continuous compounding, which expression solves for the rate \(r\%\)?
Use continuous compounding. Apply doubling condition. Solve for r.
\(200=100e^{(r/100)β 10}.\) Thus \(2=e^{r/10}.\) Taking logarithms, \(lnβ‘2=\frac{r}{10}\) and \(r=10lnβ‘2.\) Hence Option C is correct.
- Option A β Uses wrong logarithmic quantity.
- Option B β Uses \(\ln\,10\) instead of \(\ln\,2\).
- Option D β Incorrect scaling factor.
Used: Substitution
Application:
- Apply the doubling condition in the compounding model.
Final Logic:
- \(r=10lnβ‘2\).
"Double β ln2."
19
\(4\pi r^{2}dr=kdt,\)
separating variables and integrating yields a relationship primarily between:
Integrate both sides. Observe resulting expression. Identify linked variables.
The passage shows \(\frac{4\pi r^{3}}{3}=kt+C.\) The final equation directly relates \(r^{3}\)and \(t\). Therefore the primary relationship is between radius cubed and time. Hence Option D is correct.
- Option A β Volume and surface area are not the final integrated variables.
- Option B β Circumference does not appear.
- Option C β Temperature is unrelated.
Used: Contextual/Tonal Matching
Application:
- Read the integrated result directly from the passage.
Final Logic:
- Integrated equation contains \(r^{3}\)and \(t\).
"Sphere volume β rΒ³."
20
Use integrated equation. Apply initial condition. Substitute known values.
From \(\frac{4\pi r^{3}}{3}=kt+C.\) Since \(r(0)=0\), \(C=0.\) Using \(r=3\) at \(t=3\), \(\frac{4\pi (27)}{3}=3k.\) Thus \(36\pi =3k\) and \(k=12\pi .\) Hence Option A is correct.
- Option B β Equals the left side before dividing by 3.
- Option C β Arithmetic error.
- Option D β Underestimates the constant.
Used: Substitution
Application:
- Insert the given data into the integrated relation.
Final Logic:
- \(36\pi =3k\Rightarrow k=12\pi\).
"Apply conditions after integration."
