document.write( "Question 275302: let f(x)=3x-2x and g(f(x))=2x^2-3x+5. what is g(x)? \n" ); document.write( "
Algebra.Com's Answer #200852 by Edwin McCravy(20056)\"\" \"About 
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let f(x)=3x-2x and g(f(x))=2x^2-3x+5. what is g(x)?
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document.write( "I think you botched what \"%22f%28x%29%22\" equals because \"3x-2x\" is just \"x\",\r\n" );
document.write( "and if \"%22f%28x%29%22\" were merely \"x\", then \"%22g%28x%29%22\" would just be the same as\r\n" );
document.write( "\"%22g%28f%28x%29%29%22\" which would be \"2x%5E2-3x%2B5\", and that would be a silly\r\n" );
document.write( "problem.\r\n" );
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document.write( "So I will make up something else for \"%22f%28x%29%22\", since I don't believe\r\n" );
document.write( "you really meant \"%22f%28x%29%22=3x-2x\". Suppose the problem were\r\n" );
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document.write( "let \"%22f%28x%29%22=x-2\" and \"%22g%28f%28x%29%29%22=2x%5E2-3x%2B5\". what is \"%22g%28x%29%22\"?\r\n" );
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document.write( "Then \"%22g%28x%29%22\" would have to be a quadratic function, say \r\n" );
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document.write( "\"%22g%28x%29%22=Ax%5E2%2BBx%2BC\"\r\n" );
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document.write( "Then \r\n" );
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document.write( "\"%22g%28f%28x%29%29%22=A%28x-2%29%5E2%2BB%28x-2%29%2BC\"\r\n" );
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document.write( "\"%22g%28f%28x%29%29%22=A%28x%5E2-4x%2B4%29%2BBx-2B%2BC\"\r\n" );
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document.write( "\"%22g%28f%28x%29%29%22=Ax%5E2-4Ax%2B4A%2BBx-2B%2BC\"\r\n" );
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document.write( "Rearrange the terms:\r\n" );
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document.write( "\"%22g%28f%28x%29%29%22=Ax%5E2%2BBx-4Ax%2B4A-2B%2BC\"\r\n" );
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document.write( "Factor x out of the 2nd and 3rd terms on the right\r\n" );
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document.write( "\"%22g%28f%28x%29%29%22=Ax%5E2%2B%28B-4A%29x%2B4A-2B%2BC\"\r\n" );
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document.write( "Since \"%22g%28f%28x%29%29%22=2x%5E2-3x%2B5\", we equate coefficients:\r\n" );
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document.write( "\"system%28A=2%2CB-4A=-3%2C4A-2B%2BC=5%29\"\r\n" );
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document.write( "Substitute \"A=2\" into \"B-4A=-3\"\r\n" );
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document.write( "\"B-4%282%29=-3\"\r\n" );
document.write( "\"B-8=-3\"\r\n" );
document.write( "\"B=5\"\r\n" );
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document.write( "Substitute \"A=2\" and \"B=5\" into\r\n" );
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document.write( "\"4A-2B%2BC=5%29\"\r\n" );
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document.write( "\"4%282%29-2%285%29%2BC=5%29\"\r\n" );
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document.write( "\"8-10%2BC=5\"\r\n" );
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document.write( "\"-2%2BC=5\"\r\n" );
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document.write( "\"C=7\"\r\n" );
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document.write( "So \"%22g%28x%29%22=Ax%5E2%2BBx%2BC\"\r\n" );
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document.write( "becomes\r\n" );
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document.write( " \"g%28x%29=2x%5E2%2B5x%2B7\"\r\n" );
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document.write( "Edwin

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