To find the equation of a line using two given set of points, you must first find slope. To do so, we must use the slope formula:
y2 - y1 / x2 - x1
In this case:
1 - 9 / -1 - 3 = -8 / -4
- 8 / -4 = 2 (simplified)
Now we can use the point-slope formula:
y - y1 = m(x - x1)
y - 1 = 2(x + 1 )
y - 1 = 2x + 2
y = 2x + 3
In order to make 3x - y = 6 in slope intercept form, we must isolate y.
- y = -3x + 6
Note: y cannot be negative, so we'll multiply both sides by -1
( -1 ) - y = - 3x + 6 ( -1 ) = y = 3x -6
