19. 4096 The sum of the series _- 4 16 + .... , to the nearest hundredth, is: 3 3 3 3 A 1600.00 B. 1788.56 C. 1820.33 D. 1984.77 20. In a geometric sequence, to = -9375 and r = 5. Determine t1. A. 1 C. -3 B. 4 D. 5 21. For what values of a does the equation ax2 + (2a - 3)x + a = 0 have non-real roots? A. a = 3/2 B. a > 3/2 C. a = 3/4 D. a> 3/4