Question

Find the first four terms of this geometric sequence A1= 3 and r=-3

Answer 1

a(n)=-1(-3^n)

3, -9, 27, -81

Answer 2

Answer: The first four terms of the given geometric sequence are 3, -9, 27 and -81.

Step-by-step explanation: We are given to find the first four terms of the geometric sequence, where

first term is 3 and common ratio is -3.

That is

`a=3,~~~r=-3.`

We know that

the n-th term of a geometric series with first term a and common ratio r is given by

`a_n=ar^(n-1).`

Therefore, the first four terms are

`a_1=ar^(1-1)=3* (-3)^0=3,\\\\a_2=ar^(2-1)=3* (-3)^(1)=-9,\\\\a_3=ar^(3-1)=3* (-3)^2=27,\\\\a_4=ar^(4-1)=3* (-3)^3=-81.`

Thus, the first four terms of the given geometric sequence are 3, -9, 27 and -81.