Question

A cube has side length x. One side of the cube is increased by 4 inches, and another side is doubled. The volume of the new rectangular prism is 450 cubic inches. The equation 2x^3+8x^2=450 can be used to find x. Find the side length of the original cube. Use a graphing calculator and a system of equations to find the answer. A. 4 inches B. 5 inches C. 9 inches D. 10 inches

Answer 1

This equation can be obtained simply by multiplying the three dimensions of the cube.
Length = x + 4
Width = 2x
Height = x
Volume = (x + 4)(2x)(x)
450 = 2x³ + 8x²
Using a graphing calculator and plotting this, we see that the solution of this equation is 5.
Therefore, the original side was 5 inches. The answer is B