Ques. 1JEE Main 2024, 27 January (Morning Shift)
If 01 1 3+x+ 1+x dx=a+b 2+c 3, where a, b, c are rational numbers, then 2a+3b-4c is equal to :
- 10
- 7
- 4
- 8
Answer
(4) 8
Solution
Rationalise the integrand:
1 3+x+ 1+x= 3+x- 1+x(3+x)-(1+x)= 3+x- 1+x2
I= 12 23 [(3+x)3/2-(1+x)3/2 ]01
= 13 [(8-2 2)-(3 3-1) ]
=3- 23 2- 3
a=3, b=- 23, c=-1 ( a, b, c are rational)
2a+3b-4c=6-2+4=8
Answer: (4)