An equation in the slope-intercept FORM is written as y=mx+B Where m is the slope of the line and b is the y-intercept. You can use this equation to write an equation if you know the slope and the y-intercept. Example Find the equation of the line Calculate the slope between the two points m=y2−y1x2−x1=(−1)−33−(−3)=−46=−23 b = 1 We've got a value for m and a value for b. This gives us the linear function y=−23x+1 In many cases the value of b is not as easily read. In those cases, or if you're uncertain whether the line actually crosses the y-axis in this particular point you can calculate b by SOLVING the equation for b and then substituting x and y with one of your two points. We can use the example above to illustrate this. We've got the two points (-3, 3) and (3, -1). From these two points we calculated the slope m=−23 This gives us the equation y=−23x+b From this we can SOLVE the equation for b b=y+23x And if we put in the values from our first point (-3, 3) we get b=3+23⋅(−3)=3+(−2)=1 If we put in this value for b in the equation we get y=−23x+1