document.write( "Question 214899: This question I come up with the wrong answer:
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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
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document.write( "I'm having trouble working it out, I begin with this:\r
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document.write( "I start with (720/x)+(720/x+10)\r
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document.write( "Expanded it to: 17x^2 - 1270x + 7200\r
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document.write( "Speed I got next using the quadratic equation: 62.5\r
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document.write( "But thats apparently wrong, what am I doing wrong? \n" );
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Algebra.Com's Answer #162349 by Alan3354(69443)![]() ![]() 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? \n" ); document.write( "---------------- \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( "r = 80 km/hr Boston to Buffalo \n" ); document.write( "r = 90 km/hr return \n" ); document.write( " \n" ); document.write( " |