The formula for a straight line is y=mx+b, where m is the slope and b is the y-intercept.
To find out the slope, we use a formula known as rise/run.
Rise means how high a point goes between any two points and run is how far the space is between any two points.
We can see that there are two points give to us. Now we ask our self how high do we have to go to reach the second points’ height. If we count it we go five UP. Meaning that the rise is positive 5.
Now we see how far the two points are. If we count it, we go 1 space the LEFT meaning -1 since going left on a graph means x is getting smaller.
Now that we have he two values, we put them into rise/run
5/-1=-5
So our value of m is -5
Meaning y=-5x+b
We still have our value of b to find and we can do this by choosing any one point on the graph and substituting it into the equation. We know that one of our points is (3,0)
We put these into the equation
y=-5x+b
0=-15+b
b=15
Therefore, y=-5x+15
