Question

suku ke21 dari barisan 9/2,3,3/2,0,...

Answer 1

Verified answer

A = 9/2 = 4½
U2 = 3
u3 = 3/2 = 1½
barisan aritmatika dengan beda = 3 - 4½ = -1½ = -3/2

U21 = a + 20b
= 4½ + 20x(-3/2)
= 9/2 - 60/2
= -(60-9)/2
= -51/2
= -25½

Answer 2

Verified answer

9/2,3,3/2,0
a = 9/2
b = -3/2

U21 = a + (n-1) b
U21 = 9/2 + (21-1) -3/2
U21 = 9/2 + (20) -3/2
U21 = 9/2 - 60/2
U21 = -25/2