Gradient from two coordinates

Task goals

• Plot and label two coordinate points, then draw the horizontal-and-vertical gradient triangle between them.
• Find signed change in y and change in x using the same subtraction order.
• Calculate and simplify m = (y_2-y_1)/(x_2-x_1), including negative and fractional gradients.
• Recognise zero gradient when the y-values match and undefined gradient when the x-values match.
• Check that reversing both subtraction orders gives the same gradient.
• Extension: substitute one point into y = mx + c, find c, write the equation, and check the second point.