Writing Equations in Slope Intercept FormLet's first quickly review slope intercept form.
Equations that are written in slope intercept form are the easiest to graph! If you need to create a graph, this is a skill that is essential! Continue reading for a couple of examples! Example 1Write the equation for a line that has a slope of -2 and y-intercept of 5.
NOTES: I substituted the value for the slope (-2) for m and the value for the y-intercept (5) for b. The variables x and y should always remain variables when writing a linear equation. That's pretty easy, now let's look at a graph. Example 2Write an equation for the following line: 
m = 3 b = -2 y = mx+b y = 3x -2 NOTES: As I analyze the graph, I notice that the line crosses the y axis at the point, (0,-2). Therefore, my y-intercept is -2. I then count the slope from the y-intercept to another point on the line. I count up 3 and right 1. 3/1, which means that my slope is 3. This is the value for m. Just to double check that my slope is positive, I notice that as I follow the line from left to right, the line is rising. Therefore, my slope is positive! The equation for this line is: y = 3x -2 Let's look at another graph. Example 3Write an equation for the following line: 
m = -3/4 b = 3 y = mx+b y = -3/4x +3 NOTES: As I analyze the graph, I notice that the y-intercept (y value of the point where the line crosses the y axis) is 3. So 3 is my value for b. I then count the slope from the y-intercept to another point on the line. I count down 3 and right 4 (or I could count up 3 and left 4). Which means that my slope is -3/4. This is the value for m. Just to double check that my slope is negative, I notice that as I follow the line from left to right, the line is falling. Therefore, my slope is negative! The equation for this line is: y = -3/4x + 3 When you have a real world (word problem) that requires you to write an equation in slope intercept form, there are two things that you want to look for:
Use the chart below to help you organize your information as you analyze each word problem. This will help you to write your equation!
Take a look at the examples below to better clarify how this chart can help you! Example 4
Example 5
Your turn to try a few!
Writing Equations PracticeWrite a linear equation for the following:
1. A line with a slope of -4 and y-intercept of 1. 2. A line with a slope of 2/3 and y-intercept of -3. 
5. A mutual fund company charges $50 a year to hold the fund and then an additional 2% (.02) of the profits made for that year. Write an equation that could be used to determine how much one would pay to the mutual fund company in a year. Let x represent the profit and y represent the total cost. Answer Key1. y = -4x +1 2. y = 2/3x -3 3. y = -2x -3 4. y = 1/3x +2 
Yes... I know, this was pretty easy! Now you can move onto writing equations in standard form. Writing Equations Unit |
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