6 0 |( 3x + 2x + x)| dx is equal to .
Answer
17
Solution
3x + x = 2 2x x
3x + 2x + x = 2x(2 x + 1) = 2 x x(2 x + 1)
On [0, ], x 0, so
I = 0 | 3x + 2x + x| dx = 0 2 x | x(2 x + 1)| dx
Put x = t, - x dx = dt:
I = -11 2|t(2t + 1)| dt = 2 -11|2t2 + t| dt
2t2 + t 0 on [-1, - 12 ] and [0, 1]; 0 on [- 12, 0 ]
With F(t) = 2t33 + t22:
-1-1/2 = F (- 12 ) - F(-1) = 124 + 16 = 524
-1/20| | = |F(0) - F (- 12 ) | = 124
01 = F(1) = 23 + 12 = 2824
I = 2 ( 5 + 1 + 2824 ) = 176
6I = 17
Answer: 17