Question

Which term of the G.P. 1, -1/3, 1/9, -1/27, ... is -1/243?​

Answer 1

Answer:

2,22,4,… is 128?

From the question, it is given that, 

Last term =128

First-term a=2

 Then, rrr=(22)÷(2)=(22)/2=2

Then, an=arn−1

SO,128=2(2)n−127=2(2)n−127/2=(2)n−127−1=(2)n−126=(2)n−1(2)n−1=(2)12

Now, comparing the powers

n−1=12n=12+1n=13