Answer
$4$
Work Step by Step
Given $f(x)=4x+3$
The difference quotient of a function $f(x)$ can be obtained by $\frac{f(x+h)-f(x)}{h}$ provided $h\ne0$, hence
$\frac{f(x+h)-f(x)}{h} = \frac{4(x+h)+3-(4x+3)}{h}$
$=\frac{4x+4h+3-4x-3}{h}$
$=\frac{4h}{h}$
$=4$
Hence, the difference quotient is $4$
