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document.write( "The other tutor gave a linear, not quadratic solution, which is\r\n" );
document.write( "not what you want.\r\n" );
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document.write( "Since we cannot see the graph that you can see, we cannot complete\r\n" );
document.write( "your problem, for just having two point is not enough to determine\r\n" );
document.write( "a quadratic function. But I'll do something. \r\n" );
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document.write( "The general equation of a quadratic function is\r\n" );
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document.write( " f(x) = a*x² + b*x + c\r\n" );
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document.write( "Since there are three unknown constants a, b, and c, the two points you gave,\r\n" );
document.write( "(-3,-1), (-2,-4), are not enough, so I will assume that you can look and see\r\n" );
document.write( "a third point on the graph that you didn't tell us about. So I will arbitrarily\r\n" );
document.write( "assume the y-intercept is (0,-4). So I'll assume the graph you see that we\r\n" );
document.write( "cannot see is this:\r\n" );
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document.write( "Here's the graph I'm assuming:\r\n" );
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document.write( "Substitute the point (-3,-1)\r\n" );
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document.write( " f(x) = a*x² + b*x + c\r\n" );
document.write( " -1 = a*(-3)² + b*(-3) + c\r\n" );
document.write( " -1 = 9a - 3b + c\r\n" );
document.write( "9a - 3b + c = -1 \r\n" );
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document.write( "Substitute the point (-2,-4)\r\n" );
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document.write( " f(x) = a*x² + b*x + c\r\n" );
document.write( " -4 = a*(-2)² + b*(-2) + c\r\n" );
document.write( " -4 = 4a - 2b + c\r\n" );
document.write( "4a - 2b + c = -4\r\n" );
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document.write( "Substitute the point, y-intercept, that I chose arbitrarily (0,-4)\r\n" );
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document.write( " f(x) = a*x² + b*x + c\r\n" );
document.write( " -4 = a*(0)² + b*(0) + c\r\n" );
document.write( " -4 = 0a + 0b + c\r\n" );
document.write( " c = -4\r\n" );
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document.write( "So we have this system of equations:\r\n" );
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document.write( " 9a - 3b + c = -1\r\n" );
document.write( " 4a - 2b + c = -4\r\n" );
document.write( " c = -4\r\n" );
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document.write( "Solve that system and get a=1, b=2, c=-4\r\n" );
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document.write( "So the function is\r\n" );
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document.write( "f(x) = ax² + bx + c\r\n" );
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document.write( "f(x) = x² + 2x - 4\r\n" );
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document.write( "Edwin
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document.write( "![\"\"](\"/images/stars/stars-13.gif\")
