document.write( "Question 1183440: f(x) = c (x - 3)(x + 3)\r
\n" ); document.write( "\n" ); document.write( "In the quadratic equation above, c is a nonzero constant. The graph of the equation in the xy- plane is a parabola with a vertex (h,k), where k = -18. What is c? \n" ); document.write( "

Algebra.Com's Answer #813782 by ikleyn(52802) $\"\"$ $\"About$

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document.write( "The x-coordinate of the vertex is exactly half way between the roots  h =  =  = 0.\r\n" );
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document.write( "Hence, the vertex is located at  (0,-18).\r\n" );
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document.write( "It means that the value of the quadratic polynomial at x = 0 is -18.\r\n" );
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document.write( "So, we substitute x= 0 into the polynomial and equate it to -18\r\n" );
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document.write( "    c*(0-3)*(0+3 = c*(-9) = -18,\r\n" );
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document.write( "or\r\n" );
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document.write( "    -9c = -18.\r\n" );
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document.write( "It gives the value of \"c\"   c =  = 2.      ANSWER\r\n" );
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document.write( "                See the plot below\r\n" );
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document.write( "    \r\n" );
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document.write( "              Plot y = 2(x-3)*(x+3).\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved.\r
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