Question

What are the values of a 1 and r of the geometric series? 1 + 3 + 9 + 27 + 81 a 1 = 1 and r = one-third a 1 = one-third and r = 1 a 1 = 1 and r = 3 a 1 = 3 and r = 1

Answer 1

Answer:

a₁ = 1 and r = 3

Step-by-step explanation:

$1+3+9+27+81\\\\a_1=1,\ a_2=3,\ a_3=9,\ a_4=27,\ a_5=81\\\\r=\dfrac{a_{n+1}}{a_n}\Rightarrow r=\dfrac{a_2}{a_1}=\dfrac{a_3}{a_2}=\dfrac{a_4}{a_3}=\dfrac{a_5}{a_4}\\\\r=\dfrac{3}{1}=\dfrac{9}{3}=\dfrac{27}{9}=\dfrac{81}{27}=3$

Answer 2

Good evening ,

Answer:

a₁ = 1

r = 3

Step-by-step explanation:

Since it’s a geometric series then

a₁ = 1 ( because 1 is the first term of the series)

3/1 = 9/3 = 27/9 = 81/27 = 3 then r=3.

:)