(9x + 4y)^2 = (9x + 4y)(9x + 4y)= 9x 9x + 9x 4y + 4y 9x + 4y 4y= 81x^2 + 36xy + 36xy + 16y^2= 81x^2 + 72xy + 16y^2
(9x + 4y)^2 = (9x + 4y)(9x + 4y)
= 9x 9x + 9x 4y + 4y 9x + 4y 4y
= 81x^2 + 36xy + 36xy + 16y^2
= 81x^2 + 72xy + 16y^2