Step-by-step explanation:
The slope-intercept form of an equation of a line:
y = mx + b
m - slope
b - y-intercept
y = 1 - 3x = -3x + 1
slope = -3
y-intercept at 1
y = 3x - 1
slope = 3
y-intercept at -1
x - 3 = y → y = 1x - 3
slope = 1
y-intercept at -3
x + 3 = y → y = 1x + 3
slope = 1
y-intercept at 3