State the fifth and seventh terms of the sequence \(-2, -3, -4\frac{1}{2}, ...\)
MATHEMATICS
WAEC 1993
State the fifth and seventh terms of the sequence \(-2, -3, -4\frac{1}{2}, ...\)
- A. \(-\frac{81}{8}, -\frac{729}{32}\)
- B. \(\frac{8}{81}, \frac{72}{39}\)
- C. \(\frac{27}{729}, \frac{718}{39}\)
- D. \(-\frac{27}{16}, -\frac{79}{81}\)
Correct Answer: A. \(-\frac{81}{8}, -\frac{729}{32}\)
Explanation
\(-2, -3, -4\frac{1}{2}, ...\)
This is a G.P with r = 1\(\frac{1}{2}\).
\(T_{n} = ar^{n - 1}\) (terms of a G.P)
\(T_{5} = (-2)(\frac{3}{2})^{5 - 1}\)
= \(-2 \times \frac{81}{16}\)
= \(-\frac{81}{8}\)
\(T_{7} = (-2)(\frac{3}{2})^{7 - 1}\)
= \(-2 \times \frac{729}{64}\)
= \(-\frac{729}{32}\)
Post an Explanation Or Report an Error
If you see any wrong question or answer, please leave a comment below and we'll take a look. If you doubt why the selected answer is correct or need additional more details? Please drop a comment or Contact us directly. Your email address will not be published. Required fields are marked *