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Writing Equations in Slope-Intercept Form - Problem 4 6,527 views

Teacher/Instructor Alissa Fong
Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

To write an equation to describe the information in a word problem, start by writing the equation in words based on the given information. Next, turn the words into math symbols the appropriate variables for the unknowns.

Those of you who already maintain a website probably know what this kind of situation describes. Those of you who don’t have a website might want one in the future, so this is a good problem to keep in the back of your head.

To start your own website, you need to buy the domain name and also pay a monthly fee. You’re looking at a domain name that costs $8 to start and you pay $5 per month. Write an equation to describe how much you pay.

Okay I’m going to do this using my slope intercept form which looks like this. I’m going to try to get an equation in that form. I’m going to start with how much you pay. I’m going to use words; I’ll go back to letters in a second. You pay, how much do you pay? You start by paying $8, you pay that first to register the domain name, then you have to pay $5 per month, so I’m going to say you have to pay an addition $5 per month. If you were to turn this sentence kind of thing, it’s not really a sentence, no period and stuff I know, but if you were to turn these words into Math symbols, you could write it like this; y equals $8 to set up plus 5x. This is an equation in slope intercept form.

I know the 5x and 8 are kind of switched, usually the slope term comes first, so I could also write also write it like this if that makes you happy, but keep in mind because with addition you could write either number first. These are the same thing written in 2 different ways. So this is pretty cool. I could use this equation to figure out how much money I would have to pay for different varying amounts of months. This is a situation where y equals mx plus b equations can be really useful in the real world.