(a) Define the slope of a non-vertical straight line in the Cartesian plane.
(b) The points A(2,3) and B(7,3) lie on the same horizontal line. Calculate the slope of AB and explain what the numerical value of the slope tells you about the orientation of the line.
(c) Using the result obtained in part (b), generalise and show that the slope of every horizontal line is 0.
(d) Hence write the equation of the line passing through A and B in slope–intercept form.