Let us first obtain the standard form of each equation:
f(x): | using points (1,1) and (2,5)
y - 1 = [(5-1)/(2-1)] (x - 1)
y - 1 = 4x - 4
y = 4x - 3
g(x) : | using points (-2,5) and (0,-3)
y - 5 = [(-3-5)/(0+2)] (x + 2)
y - 5 = -4x -8
y = -4x - 3
h(x) = -4x + 3
j(x) = 4x + 3
In summary:
f(x) = 4x - 3
g(x) = -4x - 3
h(x) = -4x + 3
j(x) = 4x + 3
f(x) and j(x) both have the same slope, but start on different y-ordinates. g(x) and h(x) have the same slope, which is the negative of the slope of f(x) and j(x).