State the fifth and seventh terms of the sequence (-2, -3, -4frac{1}{2}, …)
-
A.
(-frac{81}{8}, -frac{729}{32}) -
B.
(frac{8}{81}, frac{72}{39}) -
C.
(frac{27}{729}, frac{718}{39}) -
D.
(-frac{27}{16}, -frac{79}{81}) -
E.
(-frac{21}{8}, frac{32}{618})
Correct Answer: Option A
Explanation
(-2, -3, -4frac{1}{2}, …)
This is a G.P with r = 1(frac{1}{2}).
(T_{n} = ar^{n – 1}) (terms of a G.P)
(T_{5} = (-2)(frac{3}{2})^{5 – 1})
= (-2 times frac{81}{16})
= (-frac{81}{8})
(T_{7} = (-2)(frac{3}{2})^{7 – 1})
= (-2 times frac{729}{64})
= (-frac{729}{32})