If t→ 0(∫₀¹ (3x + 5)^t dx)(1)/(t) = (α)/(5e)((8)/(5))(2)/(3), then α is equal to

Numerical Answer Type:
Enter a numerical value Answer: 64 to 64 +4 marks

Solution & Explanation

Related Formula

Standard indeterminacy layout resolution rules for limits matching form 1^∞:

t → 0 [g(t)](1)/(t) = e^ t → 0 (g(t) - 1)/(t)
Core Logic

Evaluate structural integration base at boundary limit initialization state t → 0:

∫₀¹ 1 dx = 1

This confirms it matches an indeterminate form of type 1^∞.

Step 1: Apply Taylor Series or L'Hopital's Theorem

Compute limits of logarithmic integration properties inside exponential power indices:

Exponent Expression = t → 0 ∫₀¹ (3x+5)^t dx - 1t

Applying L'Hopital's theorem to differentiate the numerator with respect to t yields:

∫₀¹ (3x+5)^t ln(3x+5) dx

Evaluating this at t = 0 gives:

∫₀¹ ln(3x+5) dx
Step 2: Complete the Final Form Match

Integrating via parts results in logarithmic value updates:

[ ((3x+5)ln(3x+5) - (3x+5))/(3) ]₀¹ = (8ln 8 - 5ln 5 - 3)/(3)

Passing components back through exponential foundations transforms terms to:

e(8ln 8 - 5ln 5 - 3)/(3) = ((8)/(5))(2)/(3) · ((64)/(5e))

Comparing with the target expression (α)/(5e)((8)/(5))(2)/(3) isolates the numerical solution directly: α = 64

Pattern Recognition

Treating 1^∞ structural transformations using logarithmic derivatives allows managing complex functions containing multiple integral boundaries effectively.

Chapter Mix

Class 11 Mathematics: Limits Class 12 Mathematics: Definite Integration

Reference Study Guides

More Limits Previous-Year Questions — Page 8

Q15 jee_main_2024_01_february_morning Continuity and Differentiability of Piecewise Functions
Let f:Rarrow R be defined as f(x)= cases(a-b 2x)/(x²) & , & x<0 x²+cx+2 & , & 0≤ x≤1 2x+1 & , & x>1 cases If f is continuous everywhere in R and m is the number of points where f is NOT differentiable, then m+a+b+c equals:
  • A. 1
  • B. 4
  • C. 3
  • D. 2

Solution

Related Formula

For a function to be continuous at a boundary point x = x₀, the left-hand limit, right-hand limit, and exact function value must all match:

x → x₀^- f(x) = x → x₀^+ f(x) = f(x₀)
Core Logic

Let's enforce continuity at the critical boundaries, x = 1 and x = 0:

  • Continuity at x = 1:
f(1^-) = f(1) = 1² + c(1) + 2 = 3 + c f(1^+) = 2(1) + 1 = 3

Equating both configurations: 3 + c = 3 c = 0.

  • Continuity at x = 0:
f(0^+) = f(0) = 0² + 0 + 2 = 2 f(0^-) = h → 0 (a - b (2h))/(h²)

Using the Taylor expansion (2h) = 1 - (4h²)/(2!) + (16h⁴)/(4!) - = 1 - 2h² + (2)/(3)h⁴ -

h → 0 (a - b(1 - 2h² + (2)/(3)h⁴ - ))/(h²) = h → 0 ((a-b) + 2bh² - (2)/(3)bh⁴ + )/(h²)

For the limit to exist and remain finite, the constant term must vanish: a - b = 0 a = b. The value of the limit is then equal to 2b. To satisfy continuity: 2b = 2 b = 1 a = 1.

Step 1: Checking Differentiability at x = 0

Evaluating the Left-Hand Derivative (LHD) at x = 0 using values a=1, b=1:

LHD = h → 0 (f(-h) - f(0))/(-h) = h → 0 ((1 - (2h))/(h²) - 2)/(-h) LHD = h → 0 ((2 - (2)/(3)h² + ) - 2)/(-h) = h → 0 (2)/(3)h = 0

Evaluating the Right-Hand Derivative (RHD) at x = 0:

RHD = h → 0 (f(h) - f(0))/(h) = h → 0 ((h² + 2) - 2)/(h) = h → 0 h = 0

Since LHD = RHD = 0, the function is fully differentiable at x = 0.

Step 2: Checking Differentiability at x = 1

Evaluating derivatives at x = 1 with parameter c = 0:

  • For 0 ≤ x ≤ 1, f(x) = x² + 2 f'(x) = 2x f'(1^-) = 2.
  • For x > 1, f(x) = 2x + 1 f'(x) = 2 f'(1^+) = 2.
  • Since the left derivative equals the right derivative at x = 1, the function is differentiable at x = 1.

    Thus, the function is differentiable everywhere, giving m = 0 points of non-differentiability.

Step 3: Finding the Requested Evaluation Sum

Now substitute the values m=0, a=1, b=1, c=0 into the target equation:

m + a + b + c = 0 + 1 + 1 + 0 = 2
Pattern Recognition

Sees: Continuity conditions paired with rational surd trigonometric expansion. Shortcut: When tracking indeterminate limits like (a-b 2x)/(x²), matching expansions row by row prevents typical computation errors encountered with standard L'Hopital differentiation loops.

Chapter Mix

Class 12 Mathematics: Limits, Continuity and Differentiability

Q25 jee_main_2024_01_february_morning One Sided Limits
Let {x} denote the fractional part of x and f(x)= ⁻¹(1-x²) ⁻¹(1-x)x-x³, x≠0. If L and R respectively denotes the left hand limit and the right hand limit of f(x) at x=0 then 32π²(L²+R²) is equal to
Numerical Answer. Answer: 18 to 18

Solution

Related Formula

Definition of fractional part function:

  • For x → 0^+, x = x - 0 = x.
  • For x → 0^-, x = x - (-1) = x + 1.
Core Logic

Let's evaluate the left-hand limit (L) and right-hand limit (R) separately by setting up substitution parameters around the point x=0.

Step 1: Evaluate Right Hand Limit (R)

As x → 0^+, substitute x = h where h → 0:

R = h → 0 ⁻¹(1-h²) ⁻¹(1-h)h(1-h²) = h → 0 ⁻¹(1-h²)h · ( ⁻¹11) = (π)/(2) h → 0 ⁻¹(1-h²)h

Let ⁻¹(1-h²) = θ 1-h² = θ h² = 1 - θ = 2 ²(θ/2). As h → 0, θ → 0, so h ≈ θ√(2):

R = (π)/(2) θ → 0 θ θ√(2) = π√(2)
Step 2: Evaluate Left Hand Limit (L)

As x → 0^-, let x = -h x = 1-h where h → 0:

L = h → 0 ⁻¹(1-(1-h)²) ⁻¹(1-(1-h))(1-h) - (1-h)³ L = h → 0 ⁻¹(2h-h²) ⁻¹h(1-h)[1 - (1-h)²] = h → 0 ⁻¹(0) ⁻¹h1 · (2h-h²) L = (π)/(2) h → 0 ( ⁻¹hh · (1)/(2-h) ) = (π)/(2) · 1 · (1)/(2) = (π)/(4)
Step 3: Calculate the Target Value

Substituting the computed limits L = (π)/(4) and R = π√(2) into the target expression:

32π²(L²+R²) = (32)/(π²) ( (π²)/(16) + (π²)/(2) ) = 32 ( (1)/(16) + (1)/(2) ) = 2 + 16 = 18
Pattern Recognition

Sees: Discontinuous fractional part function framing an indeterminate limit form. Trap: Be extremely careful when managing fractional limits below zero: x → 1 when x → 0^-, transforming expressions significantly compared to right-hand approaches.

Chapter Mix

Class 12 Mathematics: Limits, Continuity and Differentiability Class 11 Mathematics: Relations and Functions

Q jee_main_2024_29_january_evening Higher Order Derivatives
Let y = ₑ((1 - x²)/(1 + x²) ), -1 < x < 1. Then at x = (1)/(2), the value of 225(y' - y'') is equal to
  • A. 732
  • B. 746
  • C. 742
  • D. 736

Solution

Related Formula
y = ln(1 - x²) - ln(1 + x²)
Core Logic

Let us differentiate the simplified logarithm form:

y' = (-2x)/(1 - x²) - (2x)/(1 + x²) = -2x ( (1 + x² + 1 - x²)/(1 - x⁴) ) = (-4x)/(1 - x⁴)

Now, computing the second derivative y'' using the quotient rule:

y'' = (-4(1 - x⁴) - (-4x)(-4x³))/((1 - x⁴)²) = (-4 + 4x⁴ - 16x⁴)/((1 - x⁴)²) = (-4(1 + 3x⁴))/((1 - x⁴)²)
Step 1: Finding the Combined Value

Let us substitute x = (1)/(2) into the expressions:

1 - x⁴ = 1 - (1)/(16) = (15)/(16) y' = (-4(1/2))/(15/16) = (-2)/(15/16) = -(32)/(15) y'' = (-4(1 + 3/16))/((15/16)²) = (-4(19/16))/(225/256) = -(19)/(4) × (256)/(225) = -(19 × 64)/(225) = -(1216)/(225)
Step 2: Resolving the Target Multiplier

Compute y' - y'':

y' - y'' = -(32)/(15) - (-(1216)/(225)) = -(480)/(225) + (1216)/(225) = (736)/(225)

Multiplying this by 225:

225(y' - y'') = 225 × (736)/(225) = 736
Pattern Recognition

Always break log quotient blocks into independent terms before differentiating (ln(a)/(b) = ln a - ln b). Differentiating fractions directly invites errors.

Chapter Mix

Class 12 Mathematics: Continuity and Differentiability

Q30 jee_main_2024_29_january_evening Leibniz Rule and Limits
Let the slope of the line 45x + 5y + 3 = 0 be 27r₁ + (9r₂)/(2) for some r₁, r₂ in R. Then x arrow 3 (∫₃x (8t²)/((3r₂ x)/(2) - r₂ x² - r₁ x³ - 3x) dt) is equal to
Numerical Answer. Answer: 12 to 12

Solution

Related Formula

Using the Newton-Leibniz formula for differentiating an integral:

(d)/(dx) ( ∫ₐx f(t) dt ) = f(x)
Core Logic

The line equation is 45x + 5y + 3 = 0 y = -9x - (3)/(5). Its slope is -9. Equating the slope expressions:

27r₁ + (9r₂)/(2) = -9 3r₁ + (r₂)/(2) = -1 (i)
Step 1: Applying L'Hopital's Rule to the Limit

The limit is in the (0)/(0) form as x arrow 3. Differentiating the numerator and denominator using L'Hopital's Rule:

Limit = x arrow 3 (8x²)/((3r₂)/(2) - 2r₂ x - 3r₁ x² - 3)
Step 2: Evaluating the Target Denominator Value

Substitute x = 3 into the differentiated structure:

Denominator = (3r₂)/(2) - 6r₂ - 27r₁ - 3 = -(9r₂)/(2) - 27r₁ - 3 = -9(3r₁ + (r₂)/(2)) - 3

From equation (i), we substitute 3r₁ + (r₂)/(2) = -1:

Denominator = -9(-1) - 3 = 9 - 3 = 6

Evaluating the full limit:

Limit = (8(3)²)/(6) = (72)/(6) = 12
Pattern Recognition

L'Hopital transformations reduce parameter sets back into exact multiples of the initial constraint formula. This avoids solving for r₁ and r₂ individually.

Chapter Mix

Class 12 Mathematics: Limits, Continuity and Differentiability

Q13 jee_main_2024_27_jan_morning Continuity at a Point
Consider the function: f(x) = cases (a(7x-12-x²))/(b(x²-7x+12)) & , x < 3 (2 (x-3))/(x-[x]) & , x > 3 b & , x = 3 cases Where [x] denotes the greatest integer less than or equal to x. If S denotes the set of all ordered pairs (a, b) such that f(x) is continuous at x=3 then the number of elements in S is:
  • A. 2
  • B. Infinitely many
  • C. 4
  • D. 1

Solution

Related Formula
For continuity at x=a, x → a^- f(x) = x → a^+ f(x) = f(a) h → 0 ( h)/(h) = 1
Core Logic

We need to evaluate the Left Hand Limit (LHL) and Right Hand Limit (RHL) at x = 3. For LHL (x < 3):

f(x) = (a(7x-12-x²))/(b(x²-7x+12))

Factor the polynomials: Numerator quadratic: -(x² - 7x + 12)

f(x) = (-a(x²-7x+12))/(b(x²-7x+12)) = (-a)/(b)

Thus, x → 3^- f(x) = (-a)/(b).

Step 1: Evaluating Right Hand Limit

For RHL (x > 3), as x → 3^+, the value of the greatest integer function [x] = 3.

f(x) = (2 (x-3))/(x-[x])

Substituting [x] = 3:

x → 3^+ f(x) = x → 3^+ (2 (x-3))/(x-3)

Applying the standard limit θ → 0 ( θ)/(θ) = 1:

RHL = 2(1) = 2
Step 2: Equating Limits

For the function to be continuous at x=3, LHL = RHL = f(3). We are given f(3) = b. Therefore:

(-a)/(b) = 2 = b

From the right equation, b = 2. Substitute b into the left equation:

(-a)/(2) = 2 ⇒ a = -4
Step 3: Final Conclusion

The only ordered pair (a, b) that makes the function continuous is (-4, 2). The number of elements in the set S is 1.

Pattern Recognition

For limits involving [x] as x → k^+, you can immediately replace [x] with k. When evaluating algebraic limits where the numerator is the exact negative of the denominator, they cancel out natively leaving just the constant ratio.

Chapter Mix

Class 12 Maths: Continuity and Differentiability Class 11 Maths: Limits and Derivatives

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