geometry
posted by Anonymous .
The length of a box is 4 inches longer than its width, and the height is 2 inches shorter than the width. Which equation can you use to solve for the length of the box if the volume is 240 cubic inches? (Assume that the width of the box is x.)

width  x
length  x+4
height x2
x(x+4)(x2) = 240
x(x^2 + 2x 8) = 240
x^3 + 2x^2  8x  240 = 0
after a few trials, I found x = 6 to work.
( tried x=3,4,5,6 , no need to try any negatives or x<2)