
Tamara J. answered 03/16/13
Math Tutoring - Algebra and Calculus (all levels)
Recall the slope (m) when given two points, (x1, y1) and (x2, y2), is defined by the following formula:
Slope = m = (y2 - y1) / (x2 - x1 )
You are given the following:
m = 2
(x1, y1) = (2, 1)
(x2, y2) = (x, 9)
This means you are looking to solve for x2 in the slope formula. To do so, plug in the given values for slope and the two points into the formula:
2 = (9 - 1) / (x2 - 2)
2 = (8) / (x2 - 2)
After we cross multiply, we get the following:
2·(x2 - 2) = 8
Now we divide both sides of this equation by 2:
(2·(x2 - 2))/2 = 8/2
x2 - 2 = 4
Adding 2 to both sides of the equation, we solve for x2 :
x2 - 2 + 2 = 4 + 2
x2 = 6
Thus, for the point (x, 9), x = 6.

Katherine P.
nice explanation, Tamara! :)
03/17/13