Question

Factor. x (squared)+3xy-54y (squared)

Answer 1

(x-6y) (x+9y)

apparently my answer has to have more than 20 characters so here are some more

Answer 2

$x^2+3xy-54y^2=x^2+9xy-6xy-54y^2\\\\=x\cdot x+x\cdot9y-6y\cdot x-6y\cdot9y\\\\=x(x+9y)-6y(x+9y)=\boxed{\boxed{(x+9y)(x-6y)}}$