Question

The points (4,-10) and (r,-1) lie on a line with slope 3. Find the missing coordinate r.

Find r.

Answer 1

r = 7

Explanation:

(4 , -10) and (r, -1)

Substitute the co-ordinates in the below given equation to find the value of 'r.

`\sf \boxed{\bf Slope = (y_2-y_1)/(x_2-x_1)}`

`\sf (-1-[-10])/(r-4) = 3\\\\\\ (-1+10)/(r-4)=3\\\\\\ (9)/(r - 4 ) = 3\\\\\\Cross \ multiply,\\`

9 = 3 *(r -4)

9 = 3*r - 3*4

9 = 3r - 12

3r - 12 = 9

Add 12 to both sides,

3r = 9 + 12

3r = 21

Divide both sides by 3,

r = 21 ÷ 3

`\boxed{\bf r = 7}`