Question

A is the point with coordinates (4 6)

B is the point with coordinates (d 12)


The gradient of the line AB is 3


Work out the value of d

Answer 1

d = 6

Explanation:

Given the coordinates A(4, 6) and B(d, 12) with the gradient of AB to be 3

Gradient m = y2-y1/x2-x1

Substitute the given values

3 = 12-6/d-4

3 = 6/d-4

Cross multiply

3(d-4) = 6

Expand

3d - 3(4) = 6

3d - 12 = 6

Add 12 to both sides

3d - 12 + 12 = 6 + 12

3d = 18

Divide both sides by 3

3d/3 = 18/3

d = 6

Hence the value of d is 6