y=x+2
y=x²
先求交点
x²-x-2=0
(x-2)(x+1)=0
得 x=2 或 x=-1
所以
∫x+2-x²dx
=x²/2+2x-x³/3 [-1,2]
=2+4-8/3-(1/2-2+1/3)
=10/3+7/6
=9/2