Two questions

Which of the following is not an identity? (A) 2x -2x e = 2 sinh x 2 2 (B) cosh2x + 3sinh2x = 1 + 4sinh2x (C)(2)(e2x + 2 + e-2x) - (2)(e2x - 2 + e-2x) = 8 (D)cosh2x = 1 + sinh2x OD OC OA O B Question 20 If f(x) = x3 - 6x, and f-1(-4) = 2, find the (A) 1/5 derivative of f -1 at x = - 4. (B) 2x2 + 3 (C) 6 (D)1/6 O A OC OD O B