已知x+y=m求(2x+2y)³-(3x+3y)²的值在线等快速
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已知x+y=m求(2x+2y)³-(3x+3y)²的值在线等快速
(2x+2y)³-(3x+3y)²
=8(x+y)^3-9(x+y)^2
=8m^3-9m^2
8m³-9m²
(2x+2y)³-(3x+3y)²
=(2m)^3-(3m)^3
=8m^3-27m^3
=-19m^3
(2x+2y)³-(3x+3y)²=[2(x+y)]³-[3(x+y)]²=(2m)³-(3m)²=8m³-9m²=m²(8m-9)