Question

A manufacturer of shipping boxes has a box shaped like a cube. The side length is
(5a + 4b). What is the volume of the box in terms of a and b? Show your work.

(5a+4b)3 =(5a+4b)(5a+4b)(5a+4b) =(25a2+40ab+16b2)(5a+4b) = 125a3 + 100a2b + 200a2b + 160ab2 + 80ab2 + 64b3 = 125a3 + 300a2b + 240ab2+ 54b3


is this correct?

Answer 1

I would have accepted the answer as :

volume = (5a + 4b)^3

in your expansion , the last term in the last line should be 64b^3, you had 54b^2,
probably just a typo since the previous line was ok.

Answer 2

(5a+4b)^3 =(5a+4b)(5a+4b)(5a+4b) =(25a2+40ab+16b2)(5a+4b) = 125a^3 + 100a^2b + 200a^2b + 160ab^2 + 80ab^2 + 64b^3 = 125a^3 + 300a^2b + 240ab^2+ 64b^3

would this be correct now?:)