先化简,再求值:3x²-{5x²-【2x-(3x²-3x+x²)】+5x},其中x=二分之一

问题描述:

先化简,再求值:3x²-{5x²-【2x-(3x²-3x+x²)】+5x},其中x=二分之一

化简结果是-6x^2,带进去就好了得-3/2

原式
=3x²-{5x²-【2x-(4x²-3x)】+5x}
=3x²-[5x²-(2x-4x²+3x)+5x]
=3x²-[5x²-(5x-4x²)+5x]
=3x²-[(5x²-5x+4x²)+5x]
=3x²-9x²
=-6x²
=-6×(1/2)²
=-3/2

3x²-{5x²-【2x-(3x²-3x+x²)】+5x}
=3x²-5x²+【2x-(3x²-3x+x²)】-5x
=3x²-5x²+2x-(3x²-3x+x²)-5x
=3x²-5x²+2x-3x²+3x+x²--5x
=-6x²
x=二分之一时
原式=-3/2