Question

If $f=\left\{\right(1,3),(2,1),(3,4),(4,2\left)\right\}$ and $g=\left\{\right(1,2),(2,3),(3,4),(4,1\left)\right\}$, then find $n\left(fog\right)$.

• A. $12$
• B. $16$
• C. $4$
• D. $5$

Answer 1

The correct option is C $4$

$f\left(g\right(1\left)\right)=f\left(2\right)=1$

$f\left(g\right(2\left)\right)=f\left(3\right)=4$

$f\left(g\right(3\left)\right)=f\left(4\right)=2$

$f\left(g\right(4\left)\right)=f\left(1\right)=3$

Hence $n\left(fog\right)=4.$