先化简再求值8x²-(x-2)(3x+1)-2(x+1)(x-5),其中x=-5

问题描述:

先化简再求值8x²-(x-2)(3x+1)-2(x+1)(x-5),其中x=-5

楼上都错了

8x²-(x-2)(3x+1)-2(x+1)(x-5)
=8x²-(3x²-5x-2)-2(x²-4x-5)
=8x²-3x²+5x+2-2x²+8x+10
=3x²+13x+12
=3x(-5)²-13x5+12
=75-65+12
=22