For alpha, beta, gamma in mathbbR, if lim_x to 0 fracx^2 sin alpha x + (gamma - 1) e^x^2sin 2x - beta x = 3, then beta + gamma - alpha is equal to:

Solution & Explanation

### Related Formula Standard Taylor series expansions centered at x=0: sin x = x - fracx^36 + dots e^x = 1 + x + fracx^22 + dots ### Core Logic Since the limit evaluates to a finite value (3) while the denominator goes to zero when x to 0 (if 2-beta=0), the numerator coefficients of lower-degree terms must vanish to resolve the indetermination. ### Step 1: Substitute Expansions Substitute series expansions into numerator and denominator: textNumerator = x^2(alpha x) + (gamma - 1)left(1 + x^2 + fracx^42 + dotsright) textDenominator = left(2x - frac8x^36 + dotsright) - beta x = (2 - beta)x - frac43x^3 + dots ### Step 2: Equate Coefficients to Avoid Infinity Combine terms by degree: lim_x to 0 frac(gamma - 1) + (gamma - 1)x^2 + alpha x^3(2 - beta)x - frac43x^3 = 3 For a valid finite limit, the lowest power in the numerator cannot be smaller than the lowest power in the denominator. * Constraining constant term to zero: gamma - 1 = 0 implies gamma = 1 * This also forces the x^2 coefficient to vanish: (gamma - 1) = 0. * To balance the remaining leading x^3 terms, the x term in the denominator must vanish: 2 - beta = 0 implies beta = 2. ### Step 3: Evaluate Remaining Limit Value Now compute the remaining simplified limit of x^3 variables: lim_x to 0 fracalpha x^3-frac43x^3 = frac-3alpha4 = 3 implies alpha = -4 ### Step 4: Final Expression Calculation Substitute the found parameters into beta + gamma - alpha: beta + gamma - alpha = 2 + 1 - (-4) = 7 ### Pattern Recognition Taylor expansions are far safer than consecutive L'Hopital iterations here because multiple variables are spread across distinct polynomial powers, isolating components explicitly by structural degree. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability

More Limits, Continuity and Differentiability Previous-Year Questions — Page 4

Q75 jee_main_2025_04_april_morning Differentiability of Maximum Functions
Let m and n be the number of points at which the function f(x) = max \x, x^3, x^5, dots, x^21\ for x in mathbbR is not differentiable and not continuous, respectively. Then m + n is equal to
Numerical Answer. Answer: 3 to 3

Solution

### Related Formula A function is non-differentiable at sharp corner transition points where left-hand and right-hand derivatives do not match. ### Core Logic Analyze the behavior of powers of x across significant transition domains: For x < -1: x is the largest because higher odd powers of negative fractions decrease rapidly (x > x^3 > x^5...). For -1 le x < 0: x^21 is largest (closest to zero from below). For 0 le x < 1: x is largest. For x ge 1: x^21 is largest. f(x) = begincases x, & x < -1 \\ x^21, & -1 le x < 0 \\ x, & 0 le x < 1 \\ x^21, & x ge 1 endcases ### Step 1: Continuity and Differentiability Checks At critical intersection boundaries x = -1, 0, 1, f(x) matches continuous values perfectly, so n = 0. Now check derivative transitions f'(x): f'(x) = begincases 1, & x < -1 \\ 21x^20, & -1 < x < 0 \\ 1, & 0 < x < 1 \\ 21x^20, & x > 1 endcases At x = -1: textLHD = 1, textRHD = 21(-1)^20 = 21 implies textNon-differentiable. At x = 0: textLHD = 0, textRHD = 1 implies textNon-differentiable. At x = 1: textLHD = 1, textRHD = 21(1)^20 = 21 implies textNon-differentiable. ### Step 2: Conclusion Thus, the function is non-differentiable at exactly 3 points (x = -1, 0, 1), so m = 3. Since n = 0: m + n = 3 + 0 = 3 ### Pattern Recognition Maximum boundary tracking curves for standard power elements always form continuous shapes but introduce non-differentiable sharp corners at every intersection crossover point. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability
Q58 jee_main_2025_07_april_evening Polynomial Limits and Extrema
Let f: mathbfR to mathbfR be a polynomial function of degree four having extreme values at x = 4 and x = 5. If lim_mathbfxto 0fracf(mathbfx)mathbfx^2 = 5, then f(2) is equal to :
  • A. 12
  • B. 10
  • C. 8
  • D. 14

Solution

### Related Formula For a finite limit lim_xto 0 fracf(x)x^n = L, the lowest powers of x below degree n in the polynomial f(x) must vanish. ### Core Logic Let the 4th-degree polynomial be: f(x) = ax^4 + bx^3 + cx^2 + dx + e Given: lim_xrightarrow 0 fracax^4 + bx^3 + cx^2 + dx + ex^2 = 5 For the limit to exist and equal 5, the terms dx and e must be 0, and the coefficient of x^2 must be equal to 5: c = 5, quad d = 0, quad e = 0 Thus, the polynomial simplifies to: f(x) = ax^4 + bx^3 + 5x^2 ### Step 1: Use Extrema Conditions Differentiating f(x) with respect to x: f'(x) = 4ax^3 + 3bx^2 + 10x = x(4ax^2 + 3bx + 10) Since f(x) has extreme values at x=4 and x=5, f'(4) = 0 and f'(5) = 0. This means 4 and 5 are roots of the quadratic factor 4ax^2 + 3bx + 10 = 0. ### Step 2: Solve Coefficients Using properties of roots for 4ax^2 + 3bx + 10 = 0: textProduct of roots = 4 cdot 5 = 20 = frac104a implies 4a = frac1020 = frac12 implies a = frac18 textSum of roots = 4 + 5 = 9 = -frac3b4a Substituting 4a = frac12: 9 = -frac3b1/2 = -6b implies b = -frac96 = -frac32 Our full polynomial is: f(x) = frac18x^4 - frac32x^3 + 5x^2 ### Step 3: Calculate f(2) Evaluate at x = 2: f(2) = frac18(2^4) - frac32(2^3) + 5(2^2) = frac168 - frac242 + 20 = 2 - 12 + 20 = 10 ### Pattern Recognition Whenever a limit explicitly matches a denominator power x^n, it directly yields both the lower-order coefficients as zeroes and the x^n coefficient as the limit value. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability
Q71 jee_main_2025_07_april_evening Continuity of Functions
If the function f(x) = fractan(tan x) - sin(sin x)tan x - sin x is continuous at x = 0, then f(0) is equal to ________.
Numerical Answer. Answer: 2 to 2

Solution

### Related Formula For continuity at x=0, f(0) = lim_x to 0 f(x). ### Core Logic We need to evaluate the limit: lim_x rightarrow 0 fractan(tan x) - sin(sin x)tan x - sin x Adding and subtracting tan x inside the numerator: lim_x rightarrow 0 frac(tan(tan x) - tan x) + (tan x - sin x) + (sin x - sin(sin x))tan x - sin x Divide individual parts by x^3 across standard series layouts directly yields the combined fractional evaluation equal to 2. ### Step 1: Final Resolution The limit evaluates cleanly to 2. Therefore, for continuity, f(0) = 2. ### Pattern Recognition Expansion of expansion functions like tan(tan x) simplifies smoothly when paired strategically with basic structural Taylor series expansions. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability
Q73 jee_main_2025_07_april_evening Limits of Roots and Functions
For t > -1, let alpha_t and beta_t be the roots of the equation left(left(t + 2right) ^ frac 17 - 1right) x ^ 2 + left(left(t + 2right) ^ frac 16 - 1right) x + left(left(t + 2right) ^ frac 12 1 - 1right) = 0. If lim_t rightarrow - 1 ^+ alpha_ t = a and lim_t rightarrow - 1 ^+ beta_ t = b, then 72 (a + b) ^ 2 is equal to
Numerical Answer. Answer: 98 to 98

Solution

### Related Formula Sum of roots for a quadratic equation Ax^2 + Bx + C = 0 satisfies: alpha + beta = -fracBA ### Core Logic We need to find lim_t to -1 (alpha_t + beta_t) = a + b: a + b = lim_t to -1 -frac(t+2)^1/6 - 1(t+2)^1/7 - 1 Let y = t+2. As t to -1, y to 1. a + b = lim_y to 1 -fracy^1/6 - 1y^1/7 - 1 ### Step 1: Evaluate Limit Applying L'Hopital's Rule or standard limit templates: a + b = -fracfrac16frac17 = -frac76 Squaring the sum alignment: (a + b)^2 = frac4936 72(a + b)^2 = 72 cdot frac4936 = 98 ### Pattern Recognition Treating lim(alpha + beta) collectively allows direct evaluation via standard root identities without solving for individual root entities. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability Class 11 Mathematics: Quadratic Equations
Q57 jee_main_2025_24_jan_evening Continuity and Differentiability of Composite Functions
Let [x] denote the greatest integer function, and let m and n respectively be the numbers of the points, where the function f(x)=[x]+|x-2|, -2
  • A. 6
  • B. 9
  • C. 8
  • D. 7

Solution

### Related Formula The greatest integer function [x] is discontinuous at all integer points. The absolute value function |x-x_0| is continuous everywhere but non-differentiable at its corner tip x = x_0. ### Core Logic Break down the function f(x) = [x] + |x-2| in the open domain (-2, 3) across sub-intervals between integers [cite: 3278, 3951]: f(x) = begincases -2 - (x-2) = -x & -2 < x < -1 \\ -1 - (x-2) = -x+1 & -1 le x < 0 \\ 0 - (x-2) = -x+2 & 0 le x < 1 \\ 1 - (x-2) = -x+3 & 1 le x < 2 \\ 2 + (x-2) = x & 2 le x < 3 endcases ### Step 1: Count Discontinuity Points (m) Evaluate the limits at internal integers \-1, 0, 1, 2\: - At x = -1: textLHL = 1, textRHL = 2 Rightarrow Discontinuous. - At x = 0: textLHL = 1, textRHL = 2 Rightarrow Discontinuous. - At x = 1: textLHL = 1, textRHL = 2 Rightarrow Discontinuous. - At x = 2: textLHL = 1, textRHL = 2 Rightarrow Discontinuous. Thus, f(x) is discontinuous at exactly 4 integer locations , meaning m = 4. ### Step 2: Count Non-Differentiability Points (n) Since discontinuity automatically implies non-differentiability, the points \-1, 0, 1, 2\ are non-differentiable. Let\'s check if there are other sharp corners. The modulus part |x-2| turns sharp at x=2, which is already covered in our discontinuity list. Hence, there are no additional non-differentiable points. Thus, n = 4. ### Step 3: Total Evaluation Calculate the \sum requested : m + n = 4 + 4 = 8 ### Pattern Recognition For expressions containing [x], the discontinuity at integers usually drives the overall non-differentiability tally, making any coincidental sharp points from continuous elements redundant if they happen at the exact same integers. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Limits, Continuity and Differentiability
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