Question

A is the point with coordinates (4,6)

b is the point with coordinates (d,21)
the graident of line AB is 3
what is the value of d

Answer 1

d = 9

Explanation:

Calculate the slope of ab then equate to 3.

Calculate the slope m using the slope formula

m =
`(y_(2)-y_(1) )/(x_(2)-x_(1) )`

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

m =
`(21-6)/(d-4)` =
`(15)/(d-4)` = 3 ( multiply both sides by d - 4 )

3(d - 4) = 15 ( divide both sides by 3 )

d - 4 = 5 ( add 4 to both sides )

d = 9