Question

A geometric sequence S1 =2 and S2 = 8, Find:
a. Common difference (r)
b. Twentieth term U20

Answer 1

HERE IS THE ANSWER MATE

Answer 2

Common difference,d = s2-s1

d = 8-2

d = 6

s2 = n/2(2a+(n-1)d)

8 = 8/2(2a+(8-1)×6)

8 = 4(2a+42)

2a+42=8/4

2a = 2-42

a = -40/2

a = -20

t20 = a+(20-1)d

t20 = -20 +19×6

t20 = -20+114

t20 = -94

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