equation of the line containing the points (4, 5) and (-1, 3)

(4,5) , (-1,3).

m = (3-5) / (-1-4) = -2 / -5 = 0.4.

Y = mX + b,
Y = 0.4*4 + b = 5,
1.6 + b = 5,
b = 5 - 1.6 = 3.4.

Y = 0.4X + 3.4.