Khan/khan-exercises — Issue #15372: Algebra challenge - wrong formula
Author: KhanBugz
Created: 2012-03-04 20:28:34+00:00
State: open
Labels: firefox, other, win7

Reporter: sb@csiaz.com

A line passes through both (4,−3) and (−4,−2). Express the equation of the line in point slope form.

The formula to find the slope is: m=(y1−y2)/(x1−x2).

So, by plugging in the numbers, we get −3−(−2)4−(−4)= −18= −18

Wrong formula.
m=(y2-y1)/(x2-x1) is the correct formula.

[algebra_challenge.html?seed=47&problem=two-points (point_slope_form)](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/algebra_challenge.html?seed=47&problem=two-points&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/algebra_challenge.html?seed=47&problem=two-points&debug&activity=%5B%5B%22incorrect-activity%22%2C%22%5B%5B%5C%221%5C%22%2C%5C%22%5C%22%2C%5C%22%5C%22%5D%5D%22%2C105%5D%2C%5B%22hint-activity%22%2C%220%22%2C1%5D%2C%5B%22hint-activity%22%2C%220%22%2C2%5D%2C%5B%22hint-activity%22%2C%220%22%2C3350%5D%5D)

[[["1","",""]]]

Mozilla/5.0 (Windows NT 6.1; rv:10.0.2) Gecko/20100101 Firefox/10.0.2

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