Q48 of 74 Page 9

Find a G.P. for which sum of first two terms is -4 and the fifth term is 4 times the third term.


a + ar = -4

a(1 + r)= -4 ………..(1)

ar4 = 4ar2



r2 = 4

r = ±2

Substituting r = 2 in (1)

a(1+2) = -4

a = 

Substituting r = -2 in (2)

a(1-2) = -4

a = 4

... If a = ,r=2

or a = 4, r = -2.

More from this chapter

All 74 →
46
The sum of the first three terms of a G.P is 16 and the sum of the next three terms is 128. Determine the first term, common ratio and the sum to n terms of the G.P.

47
Given a G.P. with a = 729 and 7th term 64, determine S7.

49
If the 4th, 10th and 16th terms of a G.P. are x, y and z, respectively. Prove that x, y, z are in G.P.

50
Find the sum to n terms of the sequence 8,88,888,888,…..