Hello,

I am having a hard time understanding the difference quotient.

f(x+h)-f(x)

-----------

h

Ex: for f(x)= 8x+9

I understand that for every x, I put in 8x+9 for it, but what do i do for the first part where it is f(x+h)? Here is where I get confused. In some examples from school it becomes (x+h)^2 . How is that possible if you are supposed to plug in 8x+9 for every x? I dont get it.

Other problems I'm having trouble with

f(x)= 5x^2

f(x)= x^2+3x+9

I'm sure with a detailed explanation, i can solve these.

Thanks for yalls help