Let (a, b) be the point of intersection of the curve x^2 = 2y and the straight line y - 2x - 6 = 0 in the second quadrant. Then the integral I = int_a^b frac9x^21 + 5^x \, dx is equal to:

Solution & Explanation

### Related Formula textKing's Property: int_a^b f(x) dx = int_a^b f(a+b-x) dx ### Core Logic First, we find the coordinates of intersection in the second quadrant to determine the integration limits a and b. ### Step 1: Find points of intersection Substitute y = fracx^22 into the line equation y - 2x - 6 = 0: fracx^22 - 2x - 6 = 0 implies x^2 - 4x - 12 = 0 (x - 6)(x + 2) = 0 implies x = 6 quad textor quad x = -2 Since the point (a, b) lies in the second quadrant, x must be negative: a = -2 b = 2(a) + 6 = 2(-2) + 6 = 2 Thus, the integration limits are a = -2 and b = 2. ### Step 2: Solve the Integral using King's Property The integral is: I = int_-2^2 frac9x^21 + 5^x dx quad text--- (1) Apply King's property, substituting x to -x (since -2 + 2 - x = -x): I = int_-2^2 frac9(-x)^21 + 5^-x dx = int_-2^2 frac9x^2 cdot 5^x1 + 5^x dx quad text--- (2) Adding equations (1) and (2): 2I = int_-2^2 9x^2 left( frac1 + 5^x1 + 5^x right) dx = int_-2^2 9x^2 dx Since 9x^2 is an even function: 2I = 2 int_0^2 9x^2 dx implies I = left[ 3x^3 right]_0^2 = 3(8) - 0 = 24 ### Pattern Recognition Whenever you see an exponential denominator like 1 + c^x inside a symmetric interval definite integral [-a, a], applying King's property will almost always cancel the exponential factor cleanly when the remaining numerator is even. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Integral Calculus

More Integral Calculus Previous-Year Questions — Page 3

Q72 jee_main_2025_07_april_evening Integration by Substitution
If int left(frac1x +frac1x^3right)left(sqrt[2]3x^-24 + x^-26right)dx = - frac alpha3 (alpha + 1) left(3 x ^ beta + x ^ gammaright) ^ frac alpha + 1alpha + C, mathbfx > 0, (alpha, beta, gamma in mathbfZ), where mathbfC is the constant of integration, then alpha + beta + gamma is equal to
Numerical Answer. Answer: 19 to 19

Solution

### Related Formula Standard power integration formula rule is: int u^n \, du = fracu^n+1n+1 + C ### Core Logic Rewrite the integral by adjusting powers inside the radical container: I = int left(frac1x^2 + frac1x^4right) left(frac3x + frac1x^3right)^frac123 \, dx Let t = frac3x + frac1x^3 implies dt = -3left(frac1x^2 + frac1x^4right)\,dx. ### Step 1: Integrate Substituting t into the equation: int fract^1/23 \, dt-3 = -frac13 cdot fract^24/2324/23 = -frac233(24) t^frac2423 Comparing parameters directly yields: alpha = 23, quad beta = -1, quad gamma = -3 alpha + beta + gamma = 23 - 1 - 3 = 19 ### Pattern Recognition Pull out high powers from the root factor to seamlessly reveal a matching f'(x) substitution pair on the outside. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Integral Calculus
Q75 jee_main_2025_24_jan_evening Indefinite Integration of Algebraic Functions
If intfrac2x^2+5x+9sqrtx^2+x+1dx=xsqrtx^2+x+1+alphasqrtx^2+x+1+betalog_eleft|x+frac12+sqrtx^2+x+1right|+C where C is the constant of integration, then alpha+2beta is equal to \_\_\_\_. [cite: 3419, 3420]
Numerical Answer. Answer: 16

Solution

### Related Formula Standard integration templates for quadratic forms: int sqrtt^2 + k^2 dt = fract2sqrtt^2+k^2 + frack^22lnleft|t + sqrtt^2+k^2right| int frac1sqrtt^2 + k^2 dt = lnleft|t + sqrtt^2+k^2right| ### Core Logic Decompose the numerator using polynomial differentiation components : 2x^2 + 5x + 9 = A(x^2 + x + 1) + B(2x + 1) + C Equating coefficients dynamically yields : - For x^2: A = 2 . - For x: A + 2B = 5 Rightarrow 2 + 2B = 5 Rightarrow B = frac32 . - Constant: A + B + C = 9 Rightarrow 2 + frac32 + C = 9 Rightarrow C = frac112 . Rewrite the integrand into three parts : 2int sqrtx^2+x+1 dx + frac32int frac2x+1sqrtx^2+x+1 dx + frac112int frac1sqrtx^2+x+1 dx ### Step 1: Complete Quadratics & Integrate Format using completing the square technique: x^2 + x + 1 = left(x + frac12right)^2 + left(fracsqrt32right)^2. 1. First Integral evaluation: 2 left[ fracleft(x+frac12right)2sqrtx^2+x+1 + frac38lnleft|x+frac12+sqrtx^2+x+1right| right] = left(x+frac12right)sqrtx^2+x+1 + frac34lnleft|x+frac12+sqrtx^2+x+1right| 2. Second Integral evaluation : frac32 cdot 2sqrtx^2+x+1 = 3sqrtx^2+x+1 3. Third Integral evaluation : frac112lnleft|x+frac12+sqrtx^2+x+1right| ### Step 2: Collect Like Terms Gather and combine matching factor parameters: textTotal = left(x + frac12 + 3right)sqrtx^2+x+1 + left(frac34 + frac112right)lnleft|x+frac12+sqrtx^2+x+1right| textTotal = left(x + frac72right)sqrtx^2+x+1 + frac254lnleft|x+frac12+sqrtx^2+x+1right| = xsqrtx^2+x+1 + frac72sqrtx^2+x+1 + frac254lnleft|x+frac12+sqrtx^2+x+1right| ### Step 3: Extract Coefficients Compare directly against the given expression variables : alpha = frac72, quad beta = frac254 alpha + 2beta = frac72 + 2left(frac254right) = frac72 + frac252 = frac322 = 16 ### Pattern Recognition When dividing large numerators containing x^2 elements over quadratic square roots, using matching coefficient expansion rules prevents lengthy substitution errors completely. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Integrals
Q57 jee_main_2025_28_jan_evening Leibnitz Rule and Definite Integral
Let f be a real valued continuous function defined on the positive real axis such that g(x)=int_0^xtf(t)dt. If g(x^3)=x^6+x^7 then value of sum_r=1^15f(r^3) is:
  • A. 320
  • B. 340
  • C. 270
  • D. 310

Solution

### Related Formula Newton-Leibnitz Theorem for differentiation under integral sign: fracddx left( int_0^x tf(t) dt right) = xf(x) ### Core Logic Given: g(x) = int_0^x tf(t) dt Differentiating both sides with respect to x: g'(x) = xf(x) implies f(x) = fracg'(x)x We are given g(x^3) = x^6 + x^7. Let y = x^3 implies x = y^1/3. Substituting this into the expression for g: g(y) = (y^1/3)^6 + (y^1/3)^7 = y^2 + y^7/3 Thus, replacing y back with x: g(x) = x^2 + x^7/3 ### Step 1: Differentiate g(x) to find f(x) g'(x) = 2x + frac73x^4/3 Now find f(x): f(x) = fracg'(x)x = frac2x + frac73x^4/3x = 2 + frac73x^1/3 ### Step 2: Evaluate the Summation We need to find sum_r=1^15 f(r^3): f(r^3) = 2 + frac73(r^3)^1/3 = 2 + frac73r Now, compute the summation from r=1 to 15: sum_r=1^15 f(r^3) = sum_r=1^15 left( 2 + frac73r right) = sum_r=1^15 2 + frac73sum_r=1^15 r (2 times 15) + frac73 times frac15 times 162 30 + frac73 times 120 = 30 + 7 times 40 = 30 + 280 = 310 ### Pattern Recognition Converting g(x^3) directly into a function of variable y=x^3 prevents multi-layer chain rule complications when applying differentiation immediately. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Sequences and Series Class 12 Mathematics: Definite Integration
Q61 jee_main_2025_28_jan_evening Integration by Substitution
If f(x)=leftintfrac1x^1/4(1+x^1/4)dxright., f(0)=-6, then f(1) is equal to:
  • A. log_e2+2
  • B. 4(log_e2-2)
  • C. 2-log_e2
  • D. 4(log_e2+2)

Solution

### Related Formula Standard substitution method and logarithmic integral rule: int frac1t+1 dt = ln|t+1| + C ### Core Logic Let x = t^4 implies dx = 4t^3 dt. When substituting into the integral: f(x) = int frac4t^3t(1+t) dt = 4 int fract^21+t dt ### Step 1: Simplify the Integral Rewrite the numerator t^2 as (t^2 - 1) + 1: 4 int frac(t^2 - 1) + 11+t dt = 4 int left( frac(t-1)(t+1)1+t + frac11+t right) dt 4 int (t - 1) dt + 4 int frac1t+1 dt 4 left[ frac(t-1)^22 right] + 4 ln|t+1| + C = 2(t-1)^2 + 4 ln|t+1| + C Substitute back t = x^1/4: f(x) = 2(x^1/4 - 1)^2 + 4 ln(1 + x^1/4) + C ### Step 2: Solve for Constant C and Find f(1) Given f(0) = -6: -6 = 2(0 - 1)^2 + 4 ln(1 + 0) + C -6 = 2 + 0 + C implies C = -8 Now find f(1): f(1) = 2(1^1/4 - 1)^2 + 4 ln(1 + 1^1/4) - 8 f(1) = 2(0) + 4 ln(2) - 8 = 4 ln 2 - 8 = 4(ln 2 - 2) ### Pattern Recognition By adding and subtracting terms in the numerator (t^2-1+1), we can quickly bypass long division for polynomials and directly integrate using standard forms. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Indefinite Integration
Q10 jee_main_2024_29_january_evening Indefinite Integration
If int fracsin^frac32 x + cos^frac32 xsqrtsin^3 x cos^3 x sin (x - theta) d x = A sqrtcos theta tan x - sin theta + B sqrtcos theta - sin theta cot x + C, where C is the integration constant, then AB is equal to
  • A. 4mathrmsec(2theta)
  • B. 4sec theta
  • C. 2sec theta
  • D. 8mathrmsecmathrmec(2theta)

Solution

### Related Formula sin(x - theta) = sin x cos theta - cos x sin theta ### Core Logic Let us partition the given integral I into two clean parts I_1 and I_2: I = int fracsin^3/2 xsqrtsin^3 x cos^3 x (sin x cos theta - cos x sin theta) \, dx + int fraccos^3/2 xsqrtsin^3 x cos^3 x (sin x cos theta - cos x sin theta) \, dx Factoring out appropriate powers of sin x and cos x from inside the roots: I_1 = int fracsec^2 xsqrttan x cos theta - sin theta \, dx I_2 = int fraccsc^2 xsqrtcos theta - cot x sin theta \, dx ### Step 1: Evaluating the Integrals For I_1, substitute tan x cos theta - sin theta = t^2 implies sec^2 x \, dx = frac2t \, dtcos theta: I_1 = int frac2t \, dtt cos theta = frac2tcos theta = 2sec theta sqrttan x cos theta - sin theta For I_2, substitute cos theta - cot x sin theta = z^2 implies csc^2 x \, dx = frac2z \, dzsin theta: I_2 = int frac2z \, dzz sin theta = frac2zsin theta = 2csc theta sqrtcos theta - cot x sin theta ### Step 2: Combining Coefficients Comparing with the given expression, we find the coefficients: A = 2sec theta, quad B = 2csc theta Multiplying them together: AB = 4sec theta csc theta = frac4sin theta cos theta = frac82sin theta cos theta = 8csc(2theta) ### Pattern Recognition When integrating roots of trigonometric functions involving (x - theta), try dividing/multiplying fields by cos^n x or sin^n x to force tan x / sec^2 x templates. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Integrals

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