The general line through (a,b) and (c,d) is
(c-a)(y-b)=(d-b)(x-a)
Here that's
(1 - - 5)(y - - 5) = (4 - -5)(x - - 5)
6(y+5)=9(x+5)
6y + 30 = 9x + 45
-15 = 9x - 6y
3x - 2y = -5
Answer: 3x - 2y = -5
We could put that in slope intercept form,
2y = 3x + 5
y = (3/2) x + 5/2
Answer: y = (3/2) x + 5/2