Posted by **Katie** on Wednesday, October 7, 2009 at 5:22pm.

4x^4-18x^2=0. I have to find out what x equals by factoring. What I did was

Factor 2x^2(2x^2+-9)=0 then 2x^2(2x+3)(x+-3), resulting in -1.5 and three. But these answers are wrong according to my book. Can you show me step by step how to do this correctly? It would be a huge help!

- Algebra -
**bobpursley**, Wednesday, October 7, 2009 at 6:07pm
They are wrong.

2x^2(2x^2-9)=0

2x^2(xsqrt2-3)(xsqrt2+3)=0

so the roots are 0,0,3/sqrt2, -3/sqrt2)

- Algebra -
**Katie**, Wednesday, October 7, 2009 at 6:35pm
Why did you square root the second line? Would you please be able to explain? Thanks!

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