Factorise..8(l+m)^3 -27(l-m)^3

Answer 1

again, a difference of cubes
(2(l+m)-3(l-m))(4(l+m)^2 + 2(l_m)*3(l-m) + 9(l-m)^2)
(-l+5m)(19l^2-10lm+7m^2)

Answer 2

difference of cube pattern
8(l+m)^3 -27(l-m)^3
= (2(l+m) - 3(l-m) )(4(l+m)^2 + 6(l+m)(l-m) + 9(l-m)^2)
= (-l + 5m)(4l^2 + 8lm + 4m^2 + 6l^2 - 6m^2 + 9l^2 - 18lm + 9m^2)
= (5m - 6)(19l^2 - 10lm + 7m^2)