Perpendicular Lines for Dummies

Line slope

In any field, there are some basic facts. Failure to know and understand these facts at an almost instinctive level is a dead giveaway that a freelancer's bullshitting instead of sharing knowledge. After all, anyone can look up factoids at wikipedia and reword them, but it takes a dumbass to get them wrong. It takes a dumbass like Colby Stream, explaining for eHow readers "How to Find the Slope of Perpendicular Lines."¹ You can find the answer to this simple little algebra problem at dozens of places around the internet, though most of them (by which we mean "the trustworthy ones") were not written by a self-appointed "professional" freelancer with a BA in communication.

That communication degree is probably the reason why Colby forgot a basic math definition and passed off this misinformation in his introduction:

"Determine the slope of the first line by looking at the equation. A standard line equation is written as y = mx+b where the letter "m" is the slope, and "b" is the value of "y" where the lines will cross..."

Our house math geek suggests that the proper wording for this step is "solve the first equation for y." However, Stream commits a far more serious error in his definition of the variable b: that's not "the value of 'y' where the lines will cross," it's the line's y-intercept, the value of y where the line crosses the y axis, It has nothing to do with the second line! No matter how well Colby communicates the remainder of his content – and, to be fair, his copy-reword-paste job is correct – a dumbass mistake like that one means this answer shouldn't be trusted. A mistake so basic, one not caught by eHow's vaunted content editors, makes Colby Stream a worthy recipient of today's Dumbass of the Day.

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was   ehow.com/how_8152568_slope-perpendicular-lines.html

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