Almost certain I did It wrong:

Find and simplify the difference quotient:

F(x+h)-f(x) /h

F(x)= x^2-5x+8

(X+h)^2-5x+8-x^2-5x+8

X^2+xh+xh+h^2-10x+16-x^2 /h

=h-8x+16

you need to plug x + h into every single x , not just the first x^2

?? That's the difference quotient. the sdcond function i wrote is what im plugging in , no? Not sure what you mean

if you have f(x) =x^2 -5x +8
f(x +h) = (x+h)^2 -5(x+h) +8