Question

x^2+y^2+z^2-xy -yz-zx is always positive

Answer 1

Show that the function

z=2x2+y2+2xy−2x+2y+2

is greater than −3

I tried to factorize but couldn't get more than (x−1)2+(x+y)2+(y−1)2−(y)2.

Is there any another way to factorize or another method??