I'm going to assume the form is y=mx+b.
To find the slope of this line, use the slope formula: (y-y1)/(x-x1). That just means the slope is 4.
Now we're going to find the y intercept, where x=0. The y intercept is (0, 0), at the origin.
So, your formula would be y=4x, where 4 is the slope.
