Question

What is formula for $x^2+y^2$?

Answer 1

Formula for $x^2+y^2$:

Since,${\left(x+y\right)}^2=x^2+y^2+2xy$

Rewritten as follow:

$x^2+y^2={\left(x+y\right)}^2-2xy$

Thus, the formula for $x^2+y^2$ is $x^2+y^2={\left(x+y\right)}^2-2xy$.