Way back in October we wrote equations in slope-intercept form or equations that look like y=mx+b where m and b are numbers. The number we put in place of m was the slope and b was the y-intercept.
So if we had this line:
We find the equation by finding the y-intercept or where the line crosses the y-axis and the slope. My line crosses at (0,3). Remember that the x value for the y-intercept will always be zero so we usually just say that the y-intercept is 3. So b=3
Then we find the slope. You have two options here, both start with choosing 2 points that are easy to find the coordinates of, meaning that the line crosses a point where the grid lines also cross. I chose (-1,0) and (2,9) because I liked them. There's no magic to the points I picked, any two would work.
Method 1: Pictures
In this method I am going to draw my rise and run between my points. The rise is blue, the run is 3. I count them out and set up my ratio of rise to run.
Method 2: Formula
Either way our slope is 3 so m=3. The equation is y=3x+3
I need it in different words or a few more examples.
Purple Math
Discovery Ed This link will find them for you, please use it wisely. An answer now isn't as valuable as one on the test. If you just use this to get the answer, you won't know what to do on the test.
Kahn Academy
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