1. Tentukan beda dan barisan berikut!! a) 2,4,6,8,.. b) -2,1,4,… c) -3,-7,-11,…. d) 25,20,15,….. 2. Tentukan suku ke-20 dari barisan berikut! a) 3,1,-1,…. b) 2,

no 1 . a. b = u2- u1 = 4-2 = 2
b. b = u2 -u1 = 1- (-2) = 2
c. b = u2 -u1 = -7 - (-3) = -10
d. b = u2-u1 = 20 - 25 = -5
2. a. 3,1,-1
a = 3
b = u2-u1 = 1 - 3 = -2
U20 = a + (n-1) .b
= 3 +( 20-1). -2
= 3 + (19). -2
=3+(-38)
= 41
b. 2,5,8
a= 2
b = 5-3 = 2
un = a + ( n- 1) . b
u20= 2 + ( 20-1 ). 2
u20= 2 + 19 . 2
u20= 2+ 38
u20= 40
c. -1,-4,-7
a= -1
b = -4- (-1)= -5
un = a +(n-1) . b
u20= -1 + (20-1). -5
u20= -1 + 19. (-5)
u20= -1 + -95
u20= 94
d. 45,41,57
a= 45
b = 41-45 = -4
u20= 45+ (20-1). -4
u20= 45+ 19 . -4
u20= 45 +-76
u20= 121