The integral 0 8x dx4 2 x + 2 x is equal to
- 2 2
- 4 2
- 2
- 3 22
Answer
(1) 2 2
Solution
I = 0 8x4 2 x + 2 xdx
Using 0a f(x) dx = 0a f(a - x) dx:
I = 0 8( - x)4 2 x + 2 xdx
2I = 8 0 dx4 2 x + 2 x
I = 4 2 0 /2 dx4 2 x + 2 x (integrand symmetric about 2)
= 8 0 /2 2 x dx4 + 2 x
Put x = t:
I = 8 0 dt4 + t2 = 8 12 [ -1 t2 ]0
= 4 2 = 2 2
Answer: (1)