If the 3rd and 7th terms of a G P are 9 and 1 9... - JAMB Mathematics 2019 Question
If the 3rd and 7th terms of a G.P are 9 and 1/9 respectively. Find the common ratio.
A
\(\frac{1}{3}\)
B
\(\frac{1}{9}\)
C
\(\frac{2}{3}\)
D
\(\frac{2}{9}\)
correct option: a
\(T_n = ar^{n - 1}\) (terms of a G.P)
\(T_3 = ar^2 = 9\) ... (i)
\(T_7 = ar^6 = \frac{1}{9}\) ... (ii)
Divide (i) by (ii);
\(\frac{ar^6}{ar^2} = \frac{\frac{1}{9}}{9}\)
\(r^4 = \frac{1}{81}\)
\(r^4 = (\frac{1}{3})^4\)
\(r = \frac{1}{3}\)
Please share this, thanks:
Add your answer
No responses