Hatrack River Forum: Simple Math Question:

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Posted by Phanto (Member # 5897) on :

I saw the following problem on an episode of King of the Hill, and immediately starting doing it, but am getting weird results. I don't get what I'm doing wrong.

y + root (y - 3) - 5 = 0

I subtract root (y - 3):

y - 5 = - root (y - 3)

At this point, if I plug in 7, I get no result: 2 = -2.

I square both sides:

y^2 - 10y + 25 = y - 3

Now if I plug in 7, I get 4 = 4... what did I do wrong?

>_>

Posted by rivka (Member # 4859) on :

You forgot that roots can be positive or negative. 4 has two roots: 2 and -2.

Posted by Phanto (Member # 5897) on :

Oh, thanks.