Answer:
125a^3 + 300a^2b + 240ab^2 + 64b^3
Step-by-step 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
