SOLUTION: 10x^4-9x^2+2=0 I set x^2=u I got u=2/5 u=1/2 when I use the square root property x^2= �√(2/5) and x^2=�√(1/2), and the math lab says is wrong. Why???

Question 814150: 10x^4-9x^2+2=0
I set x^2=u
I got u=2/5
u=1/2
when I use the square root property x^2= �√(2/5) and x^2=�√(1/2), and the math lab says is wrong. Why???
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
x^2=u
10u^2-9u+2=0
x^2=2/5 not +-sqrt(2/5)
[x=+-sqrt(2/5) we don't need to know this; we never use it.]
x^2=1/2 not +-sqrt(1/2)
[x=+-sqrt(1/2) we don't need to know this; we never use it.]
check
10*1/4-9* 1/2+2=0
2.5-4.5+2=0
0=0
ok
check
10*4/25-9*2/5+2=0
40/25-18/5+2=0
8/5-18/5+10/5=0
0=0
ok

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SOLUTION: 10x^4-9x^2+2=0 I set x^2=u I got u=2/5 u=1/2 when I use the square root property x^2= �&#8730;(2/5) and x^2=�&#8730;(1/2), and the math lab says is wrong. Why???

SOLUTION: 10x^4-9x^2+2=0 I set x^2=u I got u=2/5 u=1/2 when I use the square root property x^2= �√(2/5) and x^2=�√(1/2), and the math lab says is wrong. Why???