Hello im stuck with a problem and the ONLY way i wanna solve it with a formel we suposed to use not derivate.

$\displaystyle Y=\frac{x-1}{x-2}$ on point (3,2)

the formel ima use is lim x->0 $\displaystyle \frac {f(a+h)-f(a)}{h}$and a=3

Progress:

$\displaystyle \frac{a+h-1}{a+h-1}-2/h$ it is suposed to mean that all that divide by h im trying my best with latex does not work well (notice i rewrite (3-1)/(3-2) as 2...

=$\displaystyle \frac{a+h-1-2a-2h+4}{a+h-2}/h$ (notice that h is suposed to divide all that i mean like (a/b)/(c/d) and h is the c and that in latex code is a at top and b the one down.

this is where i notice this dont work over and over... i am doing something wrong that i cant see