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

Solution & Explanation

### 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

Reference Study Guides

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Q17 jee_main_2024_31_jan_morning Continuity Check
Let g(x) be a linear function and f(x) = begincases g(x) & , x le 0 \\ left(frac1+x2+xright)^frac1x & , x > 0 endcases is continuous at x = 0. If f'(1) = f(-1), then the value of g(3) is
  • A. frac13 log_e left(frac49e^1/3right)
  • B. frac13 log_e left(frac49right) + 1
  • C. log_e left(frac49right) - 1
  • D. log_e left(frac49e^1/3right)

Solution

### Core Logic Let g(x) = ax + b. Since f(x) is continuous at x = 0: lim_x to 0^+ f(x) = f(0) lim_x to 0 left(frac1+x2+xright)^frac1x = b As x to 0, the base approaches frac12, and exponent approaches infty. Thus, left(frac12right)^infty = 0. So, b = 0. Thus, g(x) = ax. ### Step 1: Calculate Derivative For x > 0, f(x) = left(frac1+x2+xright)^frac1x. Let y = f(x). ln y = frac1x lnleft(frac1+x2+xright) Differentiating both sides w.r.t x: frac1y y' = -frac1x^2 lnleft(frac1+x2+xright) + frac1x cdot frac2+x1+x cdot frac1(2+x) - (1+x)1(2+x)^2 y' = y left[ -frac1x^2 lnleft(frac1+x2+xright) + frac1x(1+x)(2+x) right] ### Step 2: Apply Condition At x=1, y = f(1) = frac23. f'(1) = frac23 left[ -1 lnleft(frac23right) + frac16 right] = -frac23 lnleft(frac23right) + frac19 Also f(-1) = g(-1) = -a. Given f'(1) = f(-1) implies -a = -frac23 lnleft(frac23right) + frac19. a = frac23 lnleft(frac23right) - frac19 ### Step 3: Evaluate g(3) g(3) = 3a = 2 lnleft(frac23right) - frac13 g(3) = lnleft(frac49right) - frac13 = lnleft(frac49right) - ln(e^1/3) = lnleft(frac49e^1/3right) ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Continuity and Differentiability Class 12 Maths: Application of Derivatives

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