Question

Factorise 3(x+y)-9(x+y)^2

Answer 1

3(x+y)-9(x+y)^2=3(x+y){1-3(x+y)}

Answer 2

let x+y = z

then

3z-9z2

3z(1-3z)

3(x+y)[1-3(x+y)]