Q. 483.7( 3 Votes )
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
Substituting r = -2 in (2)
a(1-2) = -4
a = 4
... If a = ,r=2
or a = 4, r = -2.
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