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.

Answer 1

125a^3 + 300a^2b + 240ab^2 + 64b^3

Explanation:

The volume of a cube is the cube of the side length.

V = s^3

Here, the side length of the cube is 5a + 4b, so we cube 5a + 4b.

V = (5a + 4b)^3

V = (5a + 4b)(5a + 4b)(5a + 4b)

V = (25a^2 + 20ab + 20ab + 16b^2)(5a + 4b)

V = (25a^2 + 40ab + 16b^2)(5a + 4b)

V = 125a^3 + 100a^2b + 200a^2b + 160ab^2 + 80ab^2 + 64b^3

V = 125a^3 + 300a^2b + 240ab^2 + 64b^3