"y = mx + c, ax +by + d = 0, what"s the difference?"By this stage, we have spent a lot of time understanding how y= mx + c is a useful general form for linear equations because we can easily relate it to the value of the gradient and the y - intercept. So now we have to wonder why we might introduce another general form - ax + by + d = 0. How does this work? How do we change between one and the other and why would we...