# Algebra

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I am stuck...
find the real solutions of the equation
x to the 4th power minus 20x squared plus 64 equals 0

• Algebra -

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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