Slope-Intercept for the Dummy Algebra Student

slope of a line from two points

One of the more glaring weaknesses of the eHow.com model was that the site merely "scraped" internet searches and passed them to their cadre of freelance contributors to answer... or attempt to answer. It makes sense that someone who knows nothing about a topic would have problems constructing a search query, so some of them make little or no sense. eHow's problem was that their contributors would gleefully "answer" nonsense questions anyway, much like Bradley James Bryant "answered" the Sciencing.com query, "How to Find Y Value for the Slope of a Line."

Those among us who have passed introductory algebra simply looked at the question in wonderment: the slope of a line has no x or y value, it is merely a number. We have no idea whether Bryant understood that problem, but we do know that Bradley James would not have picked up his stipend if he had merely said, "This question makes no sense."
So, dollar signs in his eyes, Bryant proceeded to craft an answer of sorts. Brad said,

"Finding the y value is easy if you know the slope of the line and the x coordinate."

First, that's not the "Y Value for the Slope": it's the y value for a given x, which one would calculate from the equation for the line. Oh, yeah, and one also needs the intercept value to make the calculation. Here's how Bradley James got around that particular complication: "Review the equation for the slope of a line. The equation for finding the slope is: m = [y1 - y2] / [x1 - x2]. If you know x, you can solve for y to find the y value for the slope of the line... Define your variables. Graph a line with the following equation: y = -(2/3)x + 3." Wait just a minute, Bradley James! Knowing x does not mean you can calculate the slope! And where did you get that equation, anyway? While it's acceptable to throw out a sample of a slope, e.g., -2⁄3, you can't simply pick a y-intercept to go with it out of thin air!

Bryant's answer, such as it is, does little more than explain how to calculate the slope from a pair of points (which wasn't the question in the first place). Our Dumbass of the Day then proceeds to pluck a formula out of his freelancing butt, and pretend to solve it for some random x. That ain't what the clueless algebra student wanted to know, idiot.

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