m = -3
y = mx + b
y =-3x + b
To solve SUBSTITUTE the point (4,-6), where x=4, y=-6and SOLVE for b
y = -3x + b
-6= -3(4) + b
-6= -12 + b ADD 12 to both sides
6= b
The y-intercept is 6
CHECK
The equation for the line in the form y = mx + b is:
y = -3x + 6
SUBSTITUTE the point (4, -6)
-6 = -3(4) + 6
- 6 = -12 + 6
-6 = -6 it checks out