>>11006217this. you have m(x-a) = c-b. Plugging in x=a and thus b=c yields m(a-a) = c-c ==> m(0)=0 ==> 0 = 0. Oh look we're done. But OK let's say you just really have to do this limit. first realize x = (y-b)/m. Now the limit is just lim b->c ((c-b)/((y-b)/m)-a) = lim b->c ((c-b)m/(y-b-a*m)) = ((c-c)m/(y-c-a*m)) = 0*m/(y-c-a*m) = 0. So yes, the limit is 0.
