Question

x² + 2xy - 9 + y²

Answer 1

\(=\left(x+y\right)^2-9=\left(x+y-3\right)\left(x+y+3\right)\)

Answer 2

\(=x^2+2xy+y^2-9=\left(x+y\right)^2-9=\left(x+y-3\right)\left(x+y+3\right)\)

Answer 3

\(x^2+2xy-9+y^2\)

\(=\left(x^2+2xy+y^2\right)-9\)

\(=\left(x+y\right)^2-3^2\)

\(=\left(x+y-3\right)\left(x+y+3\right)\)