Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)

If int_0^1frac1sqrt3+x+sqrt1+xdx=a+bsqrt2+csqrt3, where a, b, c are rational numbers, then 2a+3b-4c is equal to:

Solution & Explanation

### Related Formula int x^n dx = fracx^n+1n+1 ### Core Logic To evaluate integrals with sum of square roots in the denominator, multiply and divide by the conjugate to rationalize it. I = int_0^1fracsqrt3+x-sqrt1+x(sqrt3+x+sqrt1+x)(sqrt3+x-sqrt1+x)dx I = int_0^1fracsqrt3+x-sqrt1+x(3+x) - (1+x)dx I = frac12 int_0^1 (sqrt3+x - sqrt1+x) dx ### Step 1: Integration and Bounds Setup Integrate the resulting expression: I = frac12 left[ frac(3+x)^3/23/2 - frac(1+x)^3/23/2 right]_0^1 I = frac12 cdot frac23 left[ (3+x)^3/2 - (1+x)^3/2 right]_0^1 I = frac13 left[ ((4)^3/2 - (2)^3/2) - ((3)^3/2 - (1)^3/2) right] ### Step 2: Term Simplification Evaluate the boundary powers: 4^3/2 = 8 2^3/2 = 2sqrt2 3^3/2 = 3sqrt3 1^3/2 = 1 Substitute back into the expression: I = frac13 [ 8 - 2sqrt2 - 3sqrt3 + 1 ] = frac13 [ 9 - 2sqrt2 - 3sqrt3 ] I = 3 - frac23sqrt2 - sqrt3 ### Step 3: Finding Co-efficients Comparing with a+bsqrt2+csqrt3 yields: a = 3, b = -frac23, c = -1 Compute 2a+3b-4c: 2(3) + 3left(-frac23right) - 4(-1) 6 - 2 + 4 = 8 ### Pattern Recognition Whenever you see a sum of square roots in the denominator of an integrand, the immediate algorithmic next step is rationalization. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Definite Integration

Reference Study Guides

More Definite Integration Previous-Year Questions — Page 2

Q68 jee_main_2025_04_april_evening Properties of Definite Integrals
Let f(x) + 2fleft(frac1xright) = x^2 + 5 and 2 mathrm g (mathrm x) - 3 mathrm g left(frac 12right) = mathrm x, mathrm x > 0. If alpha = int_ 1 ^ 2 f (x) d x, and beta = int_ 1 ^ 2 g (x) d x, then the value of 9alpha + beta is:
  • A. 1
  • B. 0
  • C. 10
  • D. 11

Solution

### Core Logic We have two functional equations to solve before integrating. Equation 1: f(x) + 2fleft(frac1xright) = x^2 + 5 Replace x with frac1x: fleft(frac1xright) + 2f(x) = frac1x^2 + 5 Multiplying this new equation by 2 and subtracting the original Equation 1 eliminates the fleft(frac1xright) term: 4f(x) + 2fleft(frac1xright) - left(f(x) + 2fleft(frac1xright)right) = 2left(frac1x^2 + 5right) - (x^2 + 5) 3f(x) = frac2x^2 - x^2 + 5 implies f(x) = frac23x^2 - fracx^23 + frac53 ### Step 1: Finding alpha Integrate f(x) from 1 to 2: alpha = int_1^2 left( frac23x^2 - fracx^23 + frac53 right) dx = left[ -frac23x - fracx^39 + frac5x3 right]_1^2 alpha = left( -frac13 - frac89 + frac103 right) - left( -frac23 - frac19 + frac53 right) = frac199 - frac89 = frac119 Thus, 9alpha = 11. ### Step 2: Solving for g(x) and finding beta We are given 2g(x) - 3gleft(frac12right) = x. Substitute x = frac12: 2gleft(frac12right) - 3gleft(frac12right) = frac12 implies -gleft(frac12right) = frac12 implies gleft(frac12right) = -frac12 Substitute this constant value back into the original equation: 2g(x) - 3left(-frac12right) = x implies 2g(x) + frac32 = x implies g(x) = fracx2 - frac34 Now find beta: beta = int_1^2 left( fracx2 - frac34 right) dx = left[ fracx^24 - frac3x4 right]_1^2 = left( 1 - frac32 right) - left( frac14 - frac34 right) = -frac12 - left(-frac12right) = 0 ### Step 3: Calculating 9alpha + beta Combining our values: 9alpha + beta = 11 + 0 = 11 ### Pattern Recognition Functional equations involving x to frac1x are easily solved by treating the swapped forms as a system of linear equations, allowing direct isolation of the underlying function. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Definite Integrals Class 12 Mathematics: Functional Equations
Q66 jee_main_2025_04_april_morning Properties of Definite Integrals
The value of int_-1^1fracleft(1 + sqrt|x| - xright)e^x + left(sqrt|x| - xright)e^-xe^x + e^-x \, mathrmdx is equal to
  • A. 3 - frac2sqrt23
  • B. 2 + frac2sqrt23
  • C. 1 - frac2sqrt23
  • D. 1 + frac2sqrt23

Solution

### Related Formula King's property of definite integrals: int_a^b f(x)mathrmdx = int_a^b f(a+b-x)mathrmdx ### Core Logic Let the given integral be I. Apply King's property by substituting x to -x: I = int_-1^1fracleft(1 + sqrt|x| + xright)e^-x + left(sqrt|x| + xright)e^xe^-x + e^x\,mathrmdx Add both integral expressions 2I = I + I: 2I = int_-1^1 frac(e^x + e^-x) + left(sqrt|x| - x + sqrt|x| + xright)(e^x + e^-x)e^x + e^-x\,mathrmdx 2I = int_-1^1 left(1 + sqrt|x| - x + sqrt|x| + xright)\,mathrmdx ### Step 1: Apply Symmetry Properties The integrand is completely even. Hence, convert intervals: 2I = 2int_0^1 left(1 + sqrt|x| - x + sqrt|x| + xright)\,mathrmdx For x in [0,1], |x| = x implies sqrt|x| - x = 0 and sqrt|x| + x = sqrt2x: I = int_0^1 (1 + sqrt2x)\,mathrmdx ### Step 2: Final Integration Execution I = left[ x + sqrt2 cdot fracx^3/23/2 right]_0^1 = left[ x + frac2sqrt23x^3/2 right]_0^1 I = 1 + frac2sqrt23 ### Pattern Recognition When functions involve combinations of exponential components (e^x, e^-x) over symmetric boundaries, adding the variable reflection eliminates exponential fractions instantly. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Definite Integration
Q52 jee_main_2025_24_jan_morning Properties of Definite Integrals
If I(m,n) = int_0^1 x^m-1 (1-x)^n-1 dx where m, n > 0, then I(9,14) + I(10,13) is :
  • A. I(9, 1)
  • B. I(19, 27)
  • C. I(1, 13)
  • D. I(9, 13)

Solution

### Related Formula The beta function integral format satisfies: I(m,n) = int_0^1 x^m-1 (1-x)^n-1 dx ### Core Logic Let's combine the terms of the requested sum directly by inserting their respective definitions: I(9,14) = int_0^1 x^9-1 (1-x)^14-1 dx = int_0^1 x^8 (1-x)^13 dx I(10,13) = int_0^1 x^10-1 (1-x)^13-1 dx = int_0^1 x^9 (1-x)^12 dx ### Step 1: Factoring out common algebraic terms Summing the two components: I(9,14) + I(10,13) = int_0^1 left[ x^8 (1-x)^13 + x^9 (1-x)^12 right] dx Factor out the common term x^8 (1-x)^12 inside the integrand: = int_0^1 x^8 (1-x)^12 left[ (1-x) + x right] dx = int_0^1 x^8 (1-x)^12 (1) dx = int_0^1 x^9-1 (1-x)^13-1 dx = I(9,13) ### Pattern Recognition When dealing with linear combinations of beta functions with shifting parameter indices, directly writing down the definite integral expression often results in immediate algebraic cancellation or simplification via basic factoring. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Definite Integrals
Q71 jee_main_2025_24_jan_morning Differentiating Under the Integral Sign
Let f be a differentiable function such that 2(x+2)^2f(x) - 3(x+2)^2 = 10int_0^x(t+2)f(t)dt for x geq 0. Then f(2) is equal to ________.
Numerical Answer. Answer: 19

Solution

### Related Formula The Leibniz Integral Rule template allows direct differentiation of an integral with variable limits: fracddxleft( int_0^x g(t) dt right) = g(x) ### Core Logic Differentiate both sides of the given functional equation with respect to x using the product rule: fracddxleft[ 2(x+2)^2 f(x) - 3(x+2)^2 right] = fracddxleft[ 10int_0^x(t+2)f(t)dt right] 4(x+2)f(x) + 2(x+2)^2 f'(x) - 6(x+2) = 10(x+2)f(x) Since x geq 0, the factor (x+2) is strictly non-zero. Divide the entire equation by 2(x+2): 2f(x) + (x+2)f'(x) - 3 = 5f(x) (x+2)f'(x) - 3f(x) = 3 ### Step 1: Solve the First-Order Differential Equation Rearrange the expression into standard linear differential equation form where y = f(x): fracdydx - frac3x+2y = frac3x+2 Compute the Integrating Factor (I.F.): textI.F. = e^int -frac3x+2 dx = e^-3ln(x+2) = (x+2)^-3 Multiply through by the I.F. and integrate: y cdot (x+2)^-3 = int frac3x+2 cdot (x+2)^-3 dx = int 3(x+2)^-4 dx fracf(x)(x+2)^3 = 3 cdot frac(x+2)^-3-3 + C = -(x+2)^-3 + C f(x) = -1 + C(x+2)^3 ### Step 2: Apply the Boundary Condition Find the boundary condition by substituting x = 0 into the original integral equation equation: 2(0+2)^2 f(0) - 3(0+2)^2 = 10 int_0^0 (t+2)f(t) dt 8f(0) - 12 = 0 implies f(0) = frac128 = frac32 Substitute x = 0 into our general solution formula: f(0) = -1 + C(0+2)^3 implies frac32 = -1 + 8C frac52 = 8C implies C = frac516 Thus, the explicit function is: f(x) = -1 + frac516(x+2)^3 ### Step 3: Evaluate at target point x = 2 Substitute x = 2 into the final function equation: f(2) = -1 + frac516(2+2)^3 = -1 + frac516(64) f(2) = -1 + 5(4) = -1 + 20 = 19 ### Pattern Recognition When an equation contains a variable integral limit int_0^x, differentiating both sides using the Leibniz rule converts it into a standard differential equation. The initial value is found by setting x = 0 directly in the original expression. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Definite Integrals Class 12 Mathematics: Differential Equations
Q62 jee_main_2025_28_jan_evening Integration by Parts
Let f:Rrightarrow R be a twice differentiable function such that f(2)=1. If F(x)=xf(x) for all xin R, leftint_0^2xF^prime(x)dx=6right. and leftint_0^2x^2F^primeprime(x)dx=40right., then F^prime(2)+leftint_0^2F(x)dxright. is equal to :
  • A. 11
  • B. 15
  • C. 6
  • D. 13

Solution

### Related Formula Integration by Parts formula: int u cdot v \, dx = u int v \, dx - int left( u' int v \, dx right) dx ### Core Logic Given F(x) = xf(x) and f(2) = 1 implies F(2) = 2f(2) = 2. Let's apply Integration by Parts to the first given integral: int_0^2 x F'(x) dx = 6 left[ xF(x) right]_0^2 - int_0^2 F(x) dx = 6 2F(2) - 0 - int_0^2 F(x) dx = 6 2(2) - int_0^2 F(x) dx = 6 implies int_0^2 F(x) dx = 4 - 6 = -2 ### Step 1: Simplify Second Integral via Integration by Parts Now look at the second integral: int_0^2 x^2 F''(x) dx = 40 Applying Integration by parts (taking u = x^2 and v = F''(x)): left[ x^2 F'(x) right]_0^2 - int_0^2 2x F'(x) dx = 40 4 F'(2) - 0 - 2 int_0^2 x F'(x) dx = 40 We already know int_0^2 x F'(x) dx = 6: 4 F'(2) - 2(6) = 40 4 F'(2) - 12 = 40 implies 4 F'(2) = 52 implies F'(2) = 13 ### Step 2: Sum the Values We need to find F'(2) + int_0^2 F(x) dx: 13 + (-2) = 11 ### Pattern Recognition Notice how the definition of f(x) is mostly a distraction to find F(2)=2. The problem is fundamentally testing consecutive applications of integration by parts to reduction structures. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Definite Integration

More Definite Integration Questions — jee_main_2024_27_jan_morning

Practice all Definite Integration previous-year questions →

YOUR FIRST PREP STEP STARTS HERE

We Map Every Repeating Question in Competitive Exams.

Say goodbye to generic mock test fatigue. RankBit uses smart analysis to group past exam questions into their foundational Repeating Question Types. Find chapter weightage, track repeating questions, and score higher with targeted practice.

Select Your Target Exam

Choose an exam track below to find formulas per chapter and patterns.

Syncing Exam Intelligence

Mapping formulas and patterns across all tracks…

PATH A — FULL LENGTH PRACTICE

Full Mock Test Hub

Simulate real NTA exam conditions with fully tracked mocks. Time yourself against past papers.

Under Development
PATH B — TARGETED PRACTICE

Topic-wise Practice Hub

Practice past-year questions one chapter at a time. Pick an exam → subject → chapter and get every PYQ for that topic — pulled together from all past papers — with the chapter's key formulas alongside.

Loading Questions... Browse Topics
Latest from the Blog
View all →

Loading articles...