化简并求值:3x3-[x3+(6x2-7x)]-2(x3-3x2-4x)其中x=-1.
问题描述:
化简并求值:3x3-[x3+(6x2-7x)]-2(x3-3x2-4x)其中x=-1.
答
原式=3x3-(x3+6x2-7x)-2x3+6x2+8x,
=3x3-x3-6x2+7x-2x3+6x2+8x,
=15x,
当x=-1时,原式=15x=15×(-1)=-15.