Use the four$-$step process to find the slope of the tangent line to the graph of the given function at any point.

$f(x)=2x^2+9x$

Step $1$:

$f(x+h)=$

Step $2$:

$f(x+h)-f(x)=$

Step $3$:

$\frac{f(x+h)-f(x)}{h}=$

Step $4$: $,f^{\text{'}}(x)=\underset{h0}{lim}\frac{f(x+h)-f(x)}{h}=$