| 120 3 0 x2 x x 4x+ 4xdx | is equal to .
Answer
15
Solution
Let g(x)= x x 4x+ 4x; g( -x)=-g(x)
Split at 2 and put x -x in the second part:
I= 0 /2 [x2-( -x)2 ]g(x)dx= 0 /2(2 x- 2)g(x)dx
∵ g ( 2-x )=g(x): 0 /2x g(x)dx= 4 0 /2g(x)dx
I= ( 22- 2 )K=- 22K, where K= 0 /2g(x)dx
∵ 4x+ 4x= 1+ 22x2
K= 0 /2 2x1+ 22xdx
Put 2x=t: K= 12 -11 dt1+t2= 12 2= 4
I=- 38
| 120 3 (- 38 ) |=15
Answer: 15