Question

Find expressions for the possible dimensions of the rectangular prism.
V = 9y^3 + 18y + 8y

Answer 1

Please explain how I can get the answer.

Answer 2

You'll want to get it to look like (y-a)(y-b)(y-c) where a, b, c are some numbers.

First: factor out the common factor y in 9y^3 + 18y + 8y

Answer 3

What do I have to do to factor out the y?

Answer 4

You have to factor it out of each term

Answer 5

eg if you had 2y^2 + 3y... factor out y to get: y(2y + 3)

Answer 6

Oh ok so it would be, y(9y^2 + 18 + 8)?

Answer 7

Yep. now you have to try to factor what's in the brackets.

Answer 8

Ok well I know 18 + 8 is 26 so that would make it, y(9y^2 + 26)

Answer 9

y(9y^2 +26) is not the answer is it?

Answer 10

i think you missed a y in here...

y(9y^2 + 18y + 8)

Answer 11

Wait, is this really the equation?
V = 9y^3 + 18y + 8y

or

V = 9y^3 + 18y^2 + 8y

Answer 12

The original problem is V = 9y^3 + 18y + 8y so wouldn't I take a y from 18y as well making it just 18?

Answer 13

Yeah... that's an odd initial function.. but yes.

Answer 14

Ok so it would be y(9y^2 + 18 + 8) ?

Answer 15

so V = y(9y^2 + 26)

which doesn't really factor with real numbers... this doesn't seem right, seems like an error in the problem. This'll only factor with imaginary numbers, which doesn't make sense for a volume of a REAL rectangular prism.

Answer 16

What did I do wrong?

Answer 17

Nothing. The problem seems wrong.

Answer 18

Because it wouldn't factor to anything that'd make sense for a rectangular prism...