using polynomials

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• Mar 27th 2009, 01:18 AM
vidalex
using polynomials
The problem states:The volume of the box is 630in^3. The height is 4 in more than the width, the length is 1 in more than than width.What is the width?

I started by forming the equation based on l*w*h=v so,

(1+w)(4+w)(w)=630 and i combined to get

w^3+5w^2+4w=630

And from this point I'm stuck
• Mar 27th 2009, 01:47 AM
craig
Your work so far is correct, rearranging the formula you have above will give you the following cubic equation:

$w^3 + 5w^2 + 4w - 630 = 0$

Have you been taught how to solve cubic equations?
• Mar 27th 2009, 02:02 AM
vidalex
No this is an extra credit problem for this unit. We've covered how to find zeros but this problem has me stumped.

Quote:

Originally Posted by craig
Your work so far is correct, rearranging the formula you have above will give you the following cubic equation:

$w^3 + 5w^2 + 4w - 630 = 0$

Have you been taught how to solve cubic equations?

• Mar 27th 2009, 05:26 AM
stapel
If you're using graphing calculators in your class, maybe you're expected to use that to find where the polynomial crosses the x-axis...?