Question

The 2nd term of an exponential sequence is 9 while the 4th term is 81.find the common ratio,the first term and the sum of the first five terms of the sequence

Answer 1

Answer:

second term: 9

4th term:81

$(3rd \: term)^{2} = 9 \times 81$

=729

$\sqrt{729} = 27$

3rd term=27

${9}^{2} = a1x27 \\ 81 = 27a1$

a1=3 the first term

$81 = 3 \times {q}^{3}$

${q}^{3} = 27$

q=3

$s = 3x \frac{1 - {3}^{5} }{1 - 3} = 364.5$