Excel Parabolas for Mathematical Dummies

Parabola formula

As our research staffers patrol the internet in search of viable candidates for the DotD (a task that actually takes about five minutes per day...), they often run across writers whose ignorance is crystalline. Such is the case of today's nominee, yet another the stable of J-school grads who "labored" for eHow.com. Today, Robert Preston reveals that he's innumerate in his Techwalla.com post, "How to Make a Parabola on Excel."¹

The weird preposition isn't Preston's fault: eHow.com's "title team" scraped search-engine queries exactly as typed, and rarely could anyone correct bad grammar. The rest of the dross in this post, though? That's on Robert.

Truth be told, Robert sort of answered the question, although it was apparent from his intro that he wasn't all that comfortable with math (or Excel):

"Excel is capable of solving equations, as well as generating graphs automatically from data provided. By combining these two functions of the program, you can quickly generate a parabolic arch graph with Excel handling all of the complex calculations."

We suspect that not many who've actually used Excel for graphing agree with either his "automatically" or his "quickly," but hey: he had to use some adjectives to get the word count up. Whatever the case, Robert walked his readers through the process of inserting a graph in your Excel table without much in the way of procedural errors, but when it came to the math? It was "Katie, bar the door!" Since all he wrote was, "Enter an equal sign followed by the formula being graphed into a cell next to the top x value..." it was obvious that Bob had no idea of the formula for a parabola. For the record, the general formula is

y = ax² + bx + c 

In its simplest form, the formula is y = x² (see image above), but clearly Preston didn't know any of that. He also didn't seem to know that the shape of the parabola curves back on itself because, for every y, there are two x values. Nope, instead Robert tells his readers,

"If you were not sure of the vertex, find the point where the change in y reversed direction then choose cells on either side of that point. For example, if y was getting larger for five cells, then smaller for the remaining cells, the vertex is between the fifth and sixth values."

Duh, duh, duh: the "vertex"² falls where the value of x reduces to zero, moron.

So, once again we find a liberal arts major, a person who studiously avoided taking any math classes after matriculating, attempting to explain mathematics. It's small wonder that Preston, like so many of his fellow "communications" majors, is our Dumbass of the Day.

¹ The original has been deleted by Leaf Group, and was never saved at archive.org. You can still read it in a slightly different form, however, at one of those #*%%@ plagiarism blogs:  excel-ask.blogspot.com/2012/12/how-to-make-parabola-on-excel.html
² The actual name of that "vertex" is the inflection point.

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