Question

(X+y)^2-9x^2

Answer 1

=(x+y-3x)(x+y+3x)

=(-2x+y)(4x+y)

Answer 2

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

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

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

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

\(=\left(4x+y\right)\left(-2x+y\right)\)