Find lim [f(x+h)-f(x)]/h

h->0

f(x) = 2 - 5x + x^2

f(x+h) = x^2 + 2 h x + h ^2 -5x - 5 h + 2

f(x) = x^2 - 5 x + 2
---------------------------------subtract
2 h x + h^2 - 5 h
divide by h
2 x + h - 5
let h-->0
2 x - 5