# Thread: Polynomial function

1. ## Polynomial function

I can't figure out how to do this problem. I tried using the quadratic formula, but ended up getting a negative under the square root. Any help would be greatly appreciated!

The target weight w for an adult man of medium build is:
w(h)=0.0728h^2 - 6.986h + 289 where h is in inches and w is in pounds. If a man of medium build has achieved his target weight of 170 lb, how tall is he?

2. Originally Posted by cam_ddrt
I can't figure out how to do this problem. I tried using the quadratic formula, but ended up getting a negative under the square root. Any help would be greatly appreciated!

The target weight w for an adult man of medium build is:
w(h)=0.0728h^2 - 6.986h + 289 where h is in inches and w is in pounds. If a man of medium build has achieved his target weight of 170 lb, how tall is he?
$\displaystyle 170=0.0728h^2 - 6.986h + 289$

$\displaystyle 0 = 0.0728h^2 - 6.986h + 119$

$\displaystyle a = 0.0728$

$\displaystyle b = -6.986$

$\displaystyle c = 119$

$\displaystyle h = \frac{-(-6.986) \pm \sqrt{(-6.986)^2 - 4(0.0728)(119)}}{2(0.0728)}$

$\displaystyle h = 73.817542...$

$\displaystyle h = 22.143996...$

which solution for $\displaystyle h$ makes sense in the context of the problem?