document.write( "Question 480707: I can't solve this.
\n" ); document.write( "15x^4 - 28x^2 + 5=0
\n" ); document.write( "The solution is x=__ \n" ); document.write( "

Algebra.Com's Answer #329174 by emargo19(101) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"u=x%5E2\"$ So $\"%28u%5E2%29%5E2=x%5E4\"$ \r
\n" ); document.write( "\n" ); document.write( " $\"15x%5E4+-+28x%5E2+%2B+5=0\"$
\n" ); document.write( " $\"15u%5E2-28u%2B5=0\"$ \r
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\n" ); document.write( "\n" ); document.write( "Using the Quadratic Formula:
\n" ); document.write( " $\"a=15\"$ $\"b=-28\"$ $\"c=5\"$
\n" ); document.write( " $\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"$
\n" ); document.write( "So
\n" ); document.write( " $\"x=+%28-%28-28%29%2B-sqrt%28%28-28%29%5E2-4%2A15%2A5%29%29%2F%282%2A15%29\"$
\n" ); document.write( " $\"x=%2828%2Bsqrt%28784-300%29%29%2F30\"$ and $\"x=%2828-sqrt%28784-300%29%29%2F30\"$
\n" ); document.write( " $\"x=%2828%2Bsqrt%28484%29%29%2F30\"$ and $\"x=%2828-sqrt%28484%29%29%2F30\"$
\n" ); document.write( " $\"x=%2828%2B22%29%2F30\"$ and $\"x=%2828-22%29%2F30\"$
\n" ); document.write( " $\"x=50%2F30\"$ and $\"x=6%2F30\"$
\n" ); document.write( " $\"x=5%2F3\"$ and $\"x=1%2F5\"$ \r
\n" ); document.write( "\n" ); document.write( "remember $\"u+=+x%5E2\"$ so:\r
\n" ); document.write( "\n" ); document.write( " $\"x+=+sqrt%285%2F3%29+=+sqrt%2815%29%2F3\"$ or $\"x+=+-sqrt%285%2F3%29+=+-sqrt%2815%29%2F3\"$ \r
\n" ); document.write( "\n" ); document.write( "or \r
\n" ); document.write( "\n" ); document.write( " $\"x+=+sqrt%281%2F5%29+=+sqrt%285%29%2F5\"$ or $\"x+=+-sqrt%281%2F5%29+=+-sqrt%285%29%2F5\"$ \r
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