(x+y+z)的二次方—(x-y-z)的二次方

问题描述:

(x+y+z)的二次方—(x-y-z)的二次方

平方差公式,x²-y²=(x+y)(x-y)

4xy+4xz

(x+y+z)^2-(x-y-z)^2
=(x+y+z+x-y-z)(x+y+z-x+y+z)
=2x(2y+2z)
=4x(y+z)
=4xy+4xz