Khan/khan-exercises — Issue #6226: Converting between slope intercept and standard form - Rejecting Correct Solutions
Author: KhanBugz
Created: 2011-11-13 19:35:07+00:00
State: open
Labels: chrome, incorrect, snowleo

Reporter: matt@w-d.org

BUG: this problem rejects correct solutions.

An Example:

Suppose I have a slope-intercept form

y = -2 x - 1

I want to find A, B, C such that
A x + B y = C
(A standard form)

One solution is

A = 1, B = 1/2, C = -1/2

The system rejects this however. I suspect the basic problem is that the exercise is coded to check whether B = -m, where m is the slope of the line in question.

However, the answers are not unique; they're only unique up to a scaler multiple...

A proper check would be whether
A / B = m and A * b = C

where m and b are the slope and intercept.

[converting_between_slope_intercept_and_standard_form.html?seed=71&problem=slope-to-standard](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/converting_between_slope_intercept_and_standard_form.html?seed=71&problem=slope-to-standard&debug)

[["1","1/2","-1/2"]]

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/14.0.835.186 Safari/535.1

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