IGNORE SOLUTIONS, THEY ARE CORRECT, I need to know how to get to the solutions.

1. (a) Find the elasticity, using calculus, of P = 2Q - 2 when Q = 4 Solution: 3/4 (b) Find the elasticity, using calculus, of P = -.50 + 10 when Q = 4 Solution: -4 (c) Find the elasticity, using calculus, of P = Q3 - 6Q + 9 when Q = 5 Solution: 1/5 2. (a) Utility Function: U = In (x) + In (y) Budget Constraint: 100 = 2x + y Find the optimal values of x and y Solution: x=25 y=50