12. Expand and simplify. (5x + 3y)²-(4x + y) (6y - x) 13. The formula V = nr³h represents the volume of a cylinder. a) Identify the variables and constant(s) in this formula. b) Which variable(s) in the formula V = ar³h would you need to set as a constant to generate i) a linear equation and ii) a quadratic equation? How should r and h be related to generate a cubic equation? c) d) Determine the radius of a cylinder with volume 600 cm³ and height 10 cm,