document.write( "Question 814150: 10x^4-9x^2+2=0
\n" ); document.write( "I set x^2=u\r
\n" ); document.write( "\n" ); document.write( "I got u=2/5
\n" ); document.write( "u=1/2
\n" ); document.write( " when I use the square root property x^2= ±√(2/5) and x^2=±√(1/2), and the math lab says is wrong. Why??? \n" ); document.write( "
Algebra.Com's Answer #490153 by richwmiller(17219)\"\" \"About 
You can put this solution on YOUR website!
x^2=u
\n" ); document.write( "10u^2-9u+2=0
\n" ); document.write( "x^2=2/5 not +-sqrt(2/5)
\n" ); document.write( "[x=+-sqrt(2/5) we don't need to know this; we never use it.]
\n" ); document.write( "x^2=1/2 not +-sqrt(1/2)
\n" ); document.write( "[x=+-sqrt(1/2) we don't need to know this; we never use it.]
\n" ); document.write( "check
\n" ); document.write( "10*1/4-9* 1/2+2=0
\n" ); document.write( "2.5-4.5+2=0
\n" ); document.write( "0=0
\n" ); document.write( "ok
\n" ); document.write( "check
\n" ); document.write( "10*4/25-9*2/5+2=0
\n" ); document.write( "40/25-18/5+2=0
\n" ); document.write( "8/5-18/5+10/5=0
\n" ); document.write( "0=0
\n" ); document.write( "ok\r
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