Question

The polynomial x 3 + 5x 2 -57x -189 expresses the volume, in cubic inches, of a shipping box, and the width is (x+3) in. If the width of the box is 15 in., what are the other two dimensions? ( Hint: The height is greater than the depth.)

A.
height: 19 in.

depth: 5 in.

B.
height: 21 in.

depth: 5 in.

C.
height: 19 in.

depth: 7 in.

D.
height: 21 in.

depth: 7 in.

Answer 1

@kriscoin @emmigrace222 @damien @Festinger @fukkedurmomhard @ceggersjr @WhisperZ

Answer 2

The question is not precise, because there are many possible values of x unless it is stated that x must be an integer.

Answer 3

If the dimensions have to be whole numbers, as shown in the the choices, then you could:
1. From x+3=15, find the value of x.
2. divide the volume expression by the width (x+3) using long division or synthetic division.
3. The quadratic resulting from step 2 can then be factorized.
4. Substitute the value of x found in step 1 into the factors found in step 3. These are the dimensions required, in inches.

Answer 4

how do i do step1

Answer 5

Solve for x, given
x+3=15
or ask
what added to 3 gives 15?

Answer 6

12

Answer 7

Great, so x=12.

Answer 8

yes

Answer 9

@mathmate

Answer 10

Were you working on step 2?

Answer 11

idk how to do any of the steps

Answer 12

For the polynomial long division, if it is not already familiar to you, you may read up on it at, for example:
http://www.purplemath.com/modules/polydiv2.htm

Then you'll need to work on factorization.
The final step is substituting x=12 in each of the factors.