Answer:
[tex]\frac{x^{2}+2xh+h^{2}}{x+h+3}[/tex]
Explanation:
Plug in (x+h) wherever you see x.
The original function is [tex]\frac{x^{2} }{x+3}[/tex]
Plug in the (x+h) into the x to get [tex]\frac{(x+h)^{2} }{(x+h)+3}[/tex]
Simplify to get [tex]\frac{x^{2}+2xh+h^{2}}{x+h+3}[/tex]