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Compound Functions

Claire2011

Posted 13 September 2011 - 06:32 PM

Functions f and g are given by f(x)=3x2 -1 and g(x)=x2+2. Find an expressions for f(g(x)).

Is the answer 3x4+5x2-2 and if so what working would i show?

Marcus

Posted 20 December 2011 - 10:50 PM

You appear to have gotten slightly confused, the answer you have is for f(x)*g(x) not f(g(x))
Solution to this problem with working should be this:

f(g(x))
=3(g(x))²-1
=3(x²+2)²-1
=3(x4+4x2+4)-1
=3x4+12x2+12-1
=3x4+12x2+11

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