Does this line pass through that square?
Python 3, 84 66 bytes

First golf, first fail (maybe).

Thanks to Rod for shaving off 18 bytes by using a function instead of direct input.

def f(a,b,c,m,n):f=-(a*m+c)/b;g=f-a/b;print(min(f,g)&lt;=n&lt;=max(f,g))


Try it online!

Explanation:

Basically we calculate the value of the line function for m and m+1, if n is inbetween the values, then the list must pass through it at some point.
Would be much better if the language had some simpler way to input multiple integers.