Question

. The sum of the first two terms of a G.P. is 36 and the product of
the first and the third terms is 9 times the second term ; find the sum of the first
8 terms.​

Answer 1

Step-by-step explanation:

$a + ar = 36 .......(1)\\ a(1 + r) = 36 \\ a \times a {r}^{2} = 9ar \\ ar \: = 9..........(2) \\ put \: 2 \: in \: 1 \\ a \: + 9 = 36 \\ a = 27 \\ so \: r \: = \frac{9}{27} = \frac{1}{3} \\ sum \: of \: 8 \: terms \: = a \frac{ 1 - {r}^{7}}{1 - r} \\ 27 \times \frac{1 - {( \frac{1}{3}) }^{7} }{1 - \frac{1}{3} } \\ = 27 \times \frac{2187 - 1}{2187} \times \frac{3}{2} \\ = \frac{1093}{27}$

Answer 2

Answer:

this is correct.................