document.write( "Question 330410: i was studying for the ACT compass test and i am having problems with functions. the question was: if f(4)=0 and f(6)=6 then which of the following could represent f(x)? The answer is 3x-12, but i do not understand how to get to that answer, what does the 4 and 6 have to do with it? thank you ahead of time \n" ); document.write( "
Algebra.Com's Answer #236816 by Edwin McCravy(20056)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "Do you know what f(4) and f(6) means?  Apparently not.\r\n" );
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document.write( "f(4) means what you get when you substitute (4) for x in the right side of \r\n" );
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document.write( "f(x) = 3x-12\r\n" );
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document.write( "If you put a (4) wherever the x is you get\r\n" );
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document.write( "f(4) = 3(4)-12 and if you simplify the right side you get\r\n" );
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document.write( "f(4) = 12-12\r\n" );
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document.write( "or\r\n" );
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document.write( "f(4) = 0\r\n" );
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document.write( "---\r\n" );
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document.write( "Similarly, f(6) means what you get when you plug 6 in for x in\r\n" );
document.write( "the right side of \r\n" );
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document.write( "f(x) = 3x-12\r\n" );
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document.write( "If you put a (6) wherever the x is you get\r\n" );
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document.write( "f(6) = 3(6)-12 and if you simplify the right side you get\r\n" );
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document.write( "f(6) = 18-12\r\n" );
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document.write( "or\r\n" );
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document.write( "f(6) = 6\r\n" );
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document.write( "--------------------\r\n" );
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document.write( "Now if you tried doing those two substitutions in any of the other\r\n" );
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document.write( "choices you had on your test you would not get 0 for f(4) and also \r\n" );
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document.write( "6 for f(6).\r\n" );
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document.write( "Learn that \"f( )\" with a number in the parentheses means \r\n" );
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document.write( "to substitute whatever number is in the parentheses for x into\r\n" );
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document.write( "the right side of the equation which has \"f(x) = ____\" where the \r\n" );
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document.write( "right side is some algebraic expression that contains x, such as\r\n" );
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document.write( "3x-12 or 6x-3 or 7x+3 or 8x²+3x-9 or etc. etc. etc.  Then after\r\n" );
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document.write( "substituting, then  simplify, and the number you get is equal \r\n" );
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document.write( "to f(that number)\r\n" );
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document.write( "Edwin
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