试说明:不论x取何值,代数式(x3+5x2+4x-1)-(-x2-3x+2x3-3)+(8-7x-6x2+x3)的值恒不变.

问题描述:

试说明:不论x取何值,代数式(x3+5x2+4x-1)-(-x2-3x+2x3-3)+(8-7x-6x2+x3)的值恒不变.

(x3+5x2+4x-1)-(-x2-3x+2x3-3)+(8-7x-6x2+x3
=x3+5x2+4x-1+x2+3x-2x3+3+8-7x-6x2+x3
=x3-2x3+x3+5x2+x2-6x2+4x+3x-7x+10
=10,
∵此代数式恒等于10,
∴不论x取何值,代数式的值是不会改变的.