document.write( "Question 924934: Hi, \r
\n" ); document.write( "\n" ); document.write( "I'm having trouble with this question from my A level Integration module;\r
\n" ); document.write( "\n" ); document.write( "Find the equation for a quadratic curve that passes through O(0,0) and its gradient at the point (-2,3) is -1.\r
\n" ); document.write( "\n" ); document.write( "I can integrate a differentiated function to get it's original, but without the differential I'm stuck on this and can't see where to begin.\r
\n" ); document.write( "\n" ); document.write( "Thanks, \r
\n" ); document.write( "\n" ); document.write( "R
\n" ); document.write( "

Algebra.Com's Answer #561206 by Fombitz(32388)\"\" \"About 
You can put this solution on YOUR website!
Quadratic curve : \"y=ax%5E2%2Bbx%2Bc\"
\n" ); document.write( "Passes through the origin :
\n" ); document.write( "\"0=a%280%29%2Bb%280%29%2Bc\"
\n" ); document.write( "\"c=0\"
\n" ); document.write( "So,
\n" ); document.write( "\"y=ax%5E2%2Bbx\"
\n" ); document.write( "The derivative of the function is,
\n" ); document.write( "\"dy%2Fdx=2ax%2Bb\"
\n" ); document.write( "The function also passes through (-2,3) where,
\n" ); document.write( "\"dy%2Fdx=-1\"
\n" ); document.write( "\"2a%28-2%29%2Bb=-1\"
\n" ); document.write( "1.\"-4a%2Bb=-1\"
\n" ); document.write( "But also from the value of the function,
\n" ); document.write( "\"3=a%28-2%29%5E2%2Bb%28-2%29\"
\n" ); document.write( "2.\"4a-2b=3\"
\n" ); document.write( "Add eq. 1 to eq. 2,
\n" ); document.write( "\"-4a%2Bb%2B4a-2b=-1%2B3\"
\n" ); document.write( "\"-b=2\"
\n" ); document.write( "\"b=-2\"
\n" ); document.write( "Then,
\n" ); document.write( "\"-4a-2=-1\"
\n" ); document.write( "\"-4a=1\"
\n" ); document.write( "\"a=-1%2F4\"
\n" ); document.write( "So then,
\n" ); document.write( "\"highlight%28y=-%281%2F4%29x%5E2-2x%29\"\r
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