Engineering
Mathematics
estimation of definite integral
Question

Let f'(x) = 192x32 + sin4πx for all x ∈R  with  f(12)=0 . If m ≤ ∫1/21f(x)dx ≤ M, then the possible values of m and M are

m = – 11, M = 0

m = 13, M = 24

m =14 , M =12

m = 1, M = 12

JEE Advance
College PredictorLive

Know your College Admission Chances Based on your Rank/Percentile, Category and Home State.

Get your JEE Main Personalised Report with Top Predicted Colleges in JoSA

Solution

f '(x) = 192x32+sin4πx∀   x∈R

Clearly f '(x) is increasing in [12,  1]

f '(x) ≤ f '(1) = 96

f '(x)≥f'(12)= 8

for maximum, f (x) = y = 96 (x−12)

for minimum, f (x) = y = 8 (x−12)

∫1/21f(x) dx≤∫1/2196(x−12) dx= 12

=∫1/21f(x) dx≥∫1/218(x−12) dx = 4x2−4x | 1/2 1= 0 – (1 – 2) = 1

∴1≤∫1/21f(x) dx≤12.