document.write( "Question 366783: What is the distance between the points where the graph of y = - 2x^2 - x + 15
\n" ); document.write( "crosses the x-axis? \n" ); document.write( "

Algebra.Com's Answer #261450 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"-2x%5E2+-+x+%2B+15\"$
\n" ); document.write( "Find the roots, which are the x-axis crossings.
\n" ); document.write( "Use quadratic formula
\n" ); document.write( " $\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"$
\n" ); document.write( " $\"a+=+-2\"$
\n" ); document.write( " $\"b+=+-1\"$
\n" ); document.write( " $\"c+=+15\"$
\n" ); document.write( " $\"x+=+%28-%28-1%29+%2B-+sqrt%28+%28-1%29%5E2-4%2A%28-2%29%2A15+%29%29%2F%282%2A%28-2%29%29+\"$
\n" ); document.write( " $\"x+=+%28+1+%2B-+sqrt%28+1+%2B+120+%29%29%2F+-4+\"$
\n" ); document.write( " $\"x+=+%281+%2B+11%29%2F-4\"$
\n" ); document.write( " $\"x+=+-3\"$
\n" ); document.write( "and
\n" ); document.write( " $\"x+=+%281+-+11%29%2F-4\"$
\n" ); document.write( " $\"x+=+5%2F2\"$
\n" ); document.write( "The difference between the roots is $\"5%2F2+-+%28-3%29+=+11%2F2\"$
\n" ); document.write( "Here's the plot:
\n" ); document.write( " $\"+graph%28+400%2C+400%2C+-5%2C+5%2C+-5%2C+20%2C+-2x%5E2+-+x+%2B+15%29+\"$ \n" ); document.write( "

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