document.write( "Question 214899: This question I come up with the wrong answer:
\n" ); document.write( "Pete drove from Buffalo to Boston, a distance of 720km. On return trip he increased his speed by 10km/h. If the total trip took 17h, what was his speed from Boston to Buffalo?\r
\n" ); document.write( "\n" ); document.write( "I'm having trouble working it out, I begin with this:\r
\n" ); document.write( "\n" ); document.write( "I start with (720/x)+(720/x+10)\r
\n" ); document.write( "\n" ); document.write( "Expanded it to: 17x^2 - 1270x + 7200\r
\n" ); document.write( "\n" ); document.write( "Speed I got next using the quadratic equation: 62.5\r
\n" ); document.write( "\n" ); document.write( "But thats apparently wrong, what am I doing wrong?
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Algebra.Com's Answer #162349 by Alan3354(69443)\"\" \"About 
You can put this solution on YOUR website!
Pete drove from Buffalo to Boston, a distance of 720km. On return trip he increased his speed by 10km/h. If the total trip took 17h, what was his speed from Boston to Buffalo?
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\n" ); document.write( "(720/r) + 720/(r+10) = 17
\n" ); document.write( "720r + 720(r+10) = 17r*(r+10)
\n" ); document.write( "1440r + 7200 = 17r^2 + 170r
\n" ); document.write( "17r^2 - 1270r - 7200 = 0
\n" ); document.write( "\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "\n" ); document.write( "
Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)
Quadratic equation \"ax%5E2%2Bbx%2Bc=0\" (in our case \"17x%5E2%2B-1270x%2B-7200+=+0\") has the following solutons:
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\n" ); document.write( " \"x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca\"
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\n" ); document.write( " For these solutions to exist, the discriminant \"b%5E2-4ac\" should not be a negative number.
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\n" ); document.write( " First, we need to compute the discriminant \"b%5E2-4ac\": \"b%5E2-4ac=%28-1270%29%5E2-4%2A17%2A-7200=2102500\".
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\n" ); document.write( " Discriminant d=2102500 is greater than zero. That means that there are two solutions: \"+x%5B12%5D+=+%28--1270%2B-sqrt%28+2102500+%29%29%2F2%5Ca\".
\n" ); document.write( "
\n" ); document.write( " \"x%5B1%5D+=+%28-%28-1270%29%2Bsqrt%28+2102500+%29%29%2F2%5C17+=+80\"
\n" ); document.write( " \"x%5B2%5D+=+%28-%28-1270%29-sqrt%28+2102500+%29%29%2F2%5C17+=+-5.29411764705882\"
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\n" ); document.write( " Quadratic expression \"17x%5E2%2B-1270x%2B-7200\" can be factored:
\n" ); document.write( " \"17x%5E2%2B-1270x%2B-7200+=+%28x-80%29%2A%28x--5.29411764705882%29\"
\n" ); document.write( " Again, the answer is: 80, -5.29411764705882.\n" ); document.write( "Here's your graph:
\n" ); document.write( "\"graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+17%2Ax%5E2%2B-1270%2Ax%2B-7200+%29\"

\n" ); document.write( "\n" ); document.write( "r = 80 km/hr Boston to Buffalo
\n" ); document.write( "r = 90 km/hr return
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