In order to calculate the value of f(3), we just need to use the value of x = 3 in the function f(x). So we have that:
[tex]\begin{gathered} f(x)=5+4x^2 \\ f(3)=5+4\cdot(3)^2 \\ f(3)=5+4\cdot9 \\ f(3)=5+36 \\ f(3)=41 \end{gathered}[/tex]Then the value of f(3) is 41.