Finding the two suitable points among $n$ points

Question

I have $n$ points in the $xy$-plane; $(x_1,y_1), \dots , (x_n,y_n)$. I want to find the following:

• the two points that form a line with greatest slope.

• the two points that form a line with least slope.

I do not know any way except to check all $C_2^n$ combinations.

Your help would be appreciated.