(1)(x+2)(x²-2x)=x³-8(2)化简并求值:(m-2)(m²+2m+4)-2m(m²-3),其中m=2
问题描述:
(1)(x+2)(x²-2x)=x³-8
(2)化简并求值:(m-2)(m²+2m+4)-2m(m²-3),其中m=2
答
(1)(x+2)(x²-2x)=x³-8x³-2x²+2x²-4x=x³-8-4x=-8∴x=2:(m-2)(m²+2m+4)-2m(m²-3)=m³-8-2m³+6m=-m³+6m-8当m=2时原式=-8+12-8=-4