document.write( "Question 62544: I had this problem on a test. I found the inverse function, but I got stuck on the checking.
\n" ); document.write( "Find the inverse function for f(x)=4x-2/3x. Check your answer.
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Algebra.Com's Answer #43312 by funmath(2933)\"\" \"About 
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Find the inverse function for f(x)=4x-2/3x. Check your answer.
\n" ); document.write( "Let f(x)=y
\n" ); document.write( "\"y=%284x-2%29%2F3x\"
\n" ); document.write( "Change the y's to x's and the x's to y's.
\n" ); document.write( "\"x=%284y-2%29%2F3y\" Solve for y.
\n" ); document.write( "\"3y%28x%29=%283y%29%284y-2%29%2F3y\"
\n" ); document.write( "\"3xy=4y-2\"
\n" ); document.write( "\"3xy-4y=-4y%2B4y-2\"
\n" ); document.write( "\"3xy-4y=-2\"
\n" ); document.write( "\"y%283x-4%29=-2\"
\n" ); document.write( "\"y%283x-4%29%2F%283x-4%29=-2%2F%283x-4%29\"
\n" ); document.write( "\"y=-2%2F%283x-4%29\"
\n" ); document.write( "let y=f^-1(x)
\n" ); document.write( "f^-1(x)=\"-2%2F%283x-4%29\"
\n" ); document.write( "To check take the f(f^-1(x)) and f^-1(f(x)) if they equal x, then they are inverses. [This is taking the composite functions. You substitute the functions into each other and simplify. If this is completely foreign to you let me know and I'll explain this more thoroughly.]
\n" ); document.write( "f(f^-1(x))=\"%284%28-2%2F%283x-4%29%29-2%29%2F%283%28-2%2F%283x-4%29%29%29\"
\n" ); document.write( "=\"%28-8%2F%283x-4%29-2%29%2F%28-6%2F%283x-4%29%29\"
\n" ); document.write( "=\"%283x-4%29%28-8%2F%283x-4%29-2%29%2F%28%283x-4%29%28-6%2F%283x-4%29%29%29\"
\n" ); document.write( "\"%28-8-2%283x-4%29%29%2F-6\"
\n" ); document.write( "\"%28-8-6x%2B8%29%2F-6\"
\n" ); document.write( "\"-6x%2F-6\"
\n" ); document.write( "\"x\" Yes!!!! This means that they are very likely inverses, but to be thorough, check f^-1(f(x))
\n" ); document.write( "f^-1(f(x))=\"-2%2F%283%28%284x-2%29%2F3x%29-4%29\"
\n" ); document.write( "=\"-2%2F%28%284x-2%29%2Fx-4%29\"
\n" ); document.write( "=\"-2x%2F%28x%284x-2%29%2Fx-4%29%29\"
\n" ); document.write( "=\"-2x%2F%284x-2-4x%29\"
\n" ); document.write( "=\"-2x%2F-2\"
\n" ); document.write( "=\"x\" Yes!!! This means that we're right!!!!
\n" ); document.write( "Happy Calculating!!!
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