1.化简求值:(5x+2x^2-3-4x^3)-(-x+3x^3-x^2),其中,x=-2 2.已知:x^2+y^2=2,xy=1/2,求

问题描述:

1.化简求值:(5x+2x^2-3-4x^3)-(-x+3x^3-x^2),其中,x=-2 2.已知:x^2+y^2=2,xy=1/2,求
(2x^2-y^2-3xy)-(x^2-2y^2+xy)的值.

(5x+2x^2-3-4x^3)-(-x+3x^3-x^2)=-7x^3+3x^2+6x-3
x=-2时 值为53



(2x^2-y^2-3xy)-(x^2-2y^2+xy)=x^2-4xy+y^2=0