当x=-3时,求8x的平方-(x-2)(x+1)-3(x-1)(x-2)的值
问题描述:
当x=-3时,求8x的平方-(x-2)(x+1)-3(x-1)(x-2)的值
答
原式=8×9-(-5)×(-2)-3×(-4)×(-5)
=72-10-60
=2
答
8x²-(x-2)(x+1)-3(x-1)(x-2)
=8x²-(x-2)[x+1+3(x-1)]
=8x²-2(x-2)(2x-1)
=2[4x²-(2x²-5x+2)]
=2(2x²+5x-2)
=2×(2×9-5×3-2)
=2