如图所示
y=x^2y=x+2x^2=x+2x^2-x-2=0(x-2)(x+1)=0x=-1 or 2A=∫(-1->2) (x+2 -x^2) dx=[(1/2)x^2+2x-(1/3)x^3]|(-1->2)=(2 +4 - 8/3) -( 1/2 -2 +1/3)=6 +2 -8/3 -5/6=8 - 7/2=9/2