Question

$\text{Find k, if}f\left(k\right)=2k-1\text{and}fof\left(k\right)=5.$

• A. 2
• B. 8
• C. 4
• D. 3

Answer 1

The correct option is A 2

$\text{Given,}f\left(k\right)=2k-1$
$fof\left(k\right)=f\left\{f\right(k\left)\right\}$
$=f\{2k-1\}=2(2k-1)-1=4k-2-1=4k-3$
$\text{Given,}fof\left(k\right)=5\therefore 4k-3=5\Rightarrow 4k=8\Rightarrow k=2$