解乘法公式计算

题目

解乘法公式计算
1·（x+y+2z）（x-y-2z）2·（x+2y-z）^2

答案

1.
=(x+(y+2z)) (x-(y+2z))
=x^2-(y+2z)^2
=x^2-y^2-4yz-4z^2
2.
=x^2+2x(2y-z)+(2y-z)^2
=x^2+4xy-2xz+4y^2-4yz+z^2
=x^2+4y^2+z^2+4xy-2xz-4yz