Question

If anyone could help me with this I'd be really grateful.

A is the point of coordinates (4,6)

B is the point with coordinates (d,21)

The gradient of the line AB is 3

Work out the value of D

Please provide a explanation

Answer 1

Answer:

d = 9

Step-by-step explanation:

Calculate the slope m of line AB and equate the result to 3

m = $\frac{y_{2}-y_{1} }{x_{2}-x_{1} }$

with (x₁, y₁ ) = A(4, 6) and (x₂, y₂ ) = B(d, 21)

m = $\frac{21-6}{d-4}$ = $\frac{15}{d-4}$ = 3 ( multiply both sides by d - 4 )

15 = 3(d - 4), that is

15 = 3d - 12 ( add 12 to both sides )

27 = 3d ( divide both sides by 3 )

9 = d