Example 1

Given the function $f:x\to <!--\; \to \; -->6x+1$. Find the value of p if $f(4)=4p+5$.

Answer:
$\begin{array}{l}f:x\to 6x+1\\ f(x)=6x+1\\ f(4)=6(4)+1\\ f(4)=25\end{array}$

$\begin{array}{l}f(4)=4p+ 5\\ 25=4p+ 5\\ 4p=25-5=20\\ p=\frac{20}{4}=5\end{array}$