# using quadratic formula to find irrational roots

• Jun 9th 2010, 10:54 PM
alessandromangione
using quadratic formula to find irrational roots
given x^4-5x^2+4...how can i use the quadratic formula to find irrational roots? i know that i need to transform x^4...but i don't know how...
thanks
• Jun 9th 2010, 11:20 PM
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Quote:

Originally Posted by alessandromangione
given x^4-5x^2+4...how can i use the quadratic formula to find irrational roots? i know that i need to transform x^4...but i don't know how...
thanks

$x^4-5x^2+4=0$

Let $y=x^2$

So $y^2-5y+4=0$

Solve for $y$, then go back and find $x$.