document.write( "Question 990509: Find the gradient of the curve x^3+4xy-y^2=15 at the point (2,1) \n" ); document.write( "
Algebra.Com's Answer #610517 by Edwin McCravy(20056)\"\" \"About 
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document.write( "Find the gradient of the curve x^3+4xy-y^2=15 at the point (2,1)\r\n" );
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document.write( "x³ + 4xy - y² = 15\r\n" );
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document.write( "3x² + 4(xy'+ y) - 2yy' = 0\r\n" );
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document.write( "3x² + 4xy' + 4y - 2yy' = 0\r\n" );
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document.write( "3x² + 4y = 2yy' - 4xy'\r\n" );
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document.write( "3x² + 4y = 2y'(y-2x)\r\n" );
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document.write( "3x² + 4y\r\n" );
document.write( "———————— = y'\r\n" );
document.write( "2(y-2x) \r\n" );
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document.write( "Substitute (2,1)\r\n" );
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document.write( "3(2)² + 4(1)\r\n" );
document.write( "———————————— = y'(2)\r\n" );
document.write( "2[(1)-2(2)] \r\n" );
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document.write( " 3(4) + 4\r\n" );
document.write( "—————————— = y'(2)\r\n" );
document.write( "  2[1-4] \r\n" );
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document.write( "  12 + 4\r\n" );
document.write( "—————————— = y'(2)\r\n" );
document.write( "   2(-3)\r\n" );
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document.write( " 16\r\n" );
document.write( "———— = y'(2)\r\n" );
document.write( " -6\r\n" );
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document.write( "   8\r\n" );
document.write( "- ——— = y'(2)\r\n" );
document.write( "   3\r\n" );
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document.write( "Edwin
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