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# If $f=\{(1,5),(2,6),(3,4)\}$ and $g=\{(4,7),(5,8),(6,9)\}$, then $gof$ = ?

$\begin{array}{1 1} \{(4,7),(5,8),(6,9),(1,5),(2,6),(3,4)\} \\ \phi \\ \{(1,8),(2,9),(3,7)\} \\ none of these\end{array}$

$f(1)=5,\:\: g(5)=8,\:\Rightarrow\:g(f(1))=8$
$Similarly \:g(f(2))=9\:\:and\:\:g(f(3))=7$
$\Rightarrow\:gof=\{(1,8),(2,9),(3,7)\}$