document.write( "Question 919994: : Let f(x)=px+q, where p and q are real numbers. Find p+q if f(f(f(x)))=8x+21. Thank you. Thank you. \n" ); document.write( "

Algebra.Com's Answer #558280 by richard1234(7193) $\"\"$ $\"About$

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f(f(f(x))) = f(f(px+q)) = f(p(px+q) + q) = p(p(px+q) + q) + q = 8x + 21\r
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\n" ); document.write( "\n" ); document.write( "We see that the x coefficient is p^3 = 8, so p = 2. If we let x = 0, for example, we have\r
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\n" ); document.write( "\n" ); document.write( "2(2(2*0 + q) + q) + q = 21
\n" ); document.write( "2(2(q) + q) + q = 21
\n" ); document.write( "7q = 21
\n" ); document.write( "q = 3 \n" ); document.write( "

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