10. Which of the following statements is true of f(x) =-13 - 6x2 -91 -2? a) f is decreasing on (-3, -1) b) f is increasing on (-3, -1) c) f is increasing on (-0o, -3) d) f is increasing on (-2,00) e) f is decreasing for all real values 11. Given that f(z) = -12 + 18 - 78 has a relative maximum at I = 9, choose the correct statement. a) f' is negative on the interval (-0o, 9) b) f' is negative on the interval (9, co) c) f' is positive on the interval (9, co) d) f' is positive on the interval (-9,co) e) f' is positive for all real values 12. Find y' given y? - 3ry + 12 = 7. 2x+ y 3y - 2x 21 2y - 3x a) 3x - 2y b) 2y - 3x C) 3 - 2y d) y e) 3y - 21