How do i do this: show that: (x+y+z)2- (x+y)2 = 2(x+y) z+z2

Work out each side.2(x+y+z)-2(x+y)(2x+2y+2z)-(2x+2y)the 2x and 2y cancel out leaving2zThen the other side2(x+y) ...... should there be a "+" before the next "z"? or is it multiplied by "2(x+y)"? ... either way, the two are not equivalent

(x+y+z)(x+y+z) - (x+y)(x+y)

x^2 + xy + xz + xy + y^2 + yz + xz + yz + z^2 - x^2 - xy - xy - y^2

terms that cancel out (x^2, xy, xy, y^2), leaving

xz + yz + xz + z^2, or rearranging terms, z^2 + 2xz + yz

... wait a minute, so, is the right side 2(x+y)^z + z^2 ??