Verticle asymptote at x=1 means that
Assuming that x>b (or else, the function is undefined), the only way to have such a limit at x=1 is that 1-b=0
Then, replace the coordinates of the points to get a and c.
1. The points (3,10) and (5,12) lie on the graph of the function with rule y=a loge (x-b) +c. The graph has a verticle asymptote with equation x=1. find the values of a,b,c
2. The graph of the function with rule f(x)= a loge (-x)+b passes through the points (-2,6) and (-4,8). Find the values of a and b