If the second term of a GP is 2 and the sum of infinite terms is 8, then the first term is
If the second term of a GP is 2 and the sum of infinite terms is 8, then the first term is
A) 8
B) 6
C) 4
D) 3
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Correct option is (C) 4
Given that second term of a GP is 2.
\(\therefore ar=2\) _____________(1)
Also given that the sum of infinite terms is 8.
\(\therefore\frac a{1-r}=8\)
\(\Rightarrow\frac a{1-\frac2a}=8\) (From (1))
\(\Rightarrow\frac{a^2}{a-2}=8\)
\(\Rightarrow a^2=8a-16\)
\(\Rightarrow a^2-8a+16=0\)
\(\Rightarrow(a-4)^2=0\)
\(\Rightarrow a-4=0\)
\(\Rightarrow a=4\)
Hence, the first term of G.P. is 4.
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