运用乘法公式计算:(1)(x-y)(x+y)-(2x-y)²
问题描述:
运用乘法公式计算:(1)(x-y)(x+y)-(2x-y)²
答
(x-y)(x+y)-(2x-y)²
=x^2-y^2-4x^2+4xy+y^2
=-y^2-4x^2+4xy
=-(y^2+4x^2-4xy)
=(y-2x)^2
答
X2+Y2-2X2+2XY-Y2=-X2+2XY
有 平方