(z+x+y)(z-x-y) 计算题!

问题描述:

(z+x+y)(z-x-y) 计算题!

(z+x+y)(z-x-y) =[z+(x+y)][z-(x+y)]=z^2-(x+y)^2=z^2-[x^2+y^2+2xy]=z^2-x^2-y^2-2xy
"^2"为平方