P(2, -8) and Q(1, y)
Gradient of slope(m) = y2−y1x2−x1\;\frac{y_2 - y_1}{x_2 - x_1}x2−x1y2−y1
- 4 = y−(−8))1−2\;\frac{y - (-8))}{1 - 2}1−2y−(−8))
-4 = y+8−1\;\frac{y + 8}{- 1}−1y+8
cross multiplying
4 = y + 8
y = 4 - 8 = -4
