Posted by **Kyle** on Wednesday, December 8, 2010 at 1:36am.

I am stuck...

find the real solutions of the equation

x to the 4th power minus 20x squared plus 64 equals 0

- Algebra -
**drwls**, Wednesday, December 8, 2010 at 2:17am
It is easier to do algebra if you write equations like that as follows:

x^4 -20x^2 +64 = 0

Make a substitution y = x^2 and you have

y^2 -20y +64 = 0

which can be factored to give

(y -16)(y-4) = 0

The solutions are:

y = x^2 = 4 or 16

So

x = +2, -2, +4 and -4.

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