You will end up with an equation with the form y = mx + c you should be familiar with from GCSE First you would need to differentiate the equation of the line For example if you had f(x) = x3 + 2x and the coordinates (3,1) you get f'(x) = 3x2 + 2 Next input the values of x and y to gain the value of "m", You will get m = 5 Now, inputting the values of x, y and m you should finally obtain the value for c, in this case it would be -2