Question

Find the 13th term of the geometric sequence 4, -8, 16​

Answer 1

Answer: The Answer is 16384 (Pay attention to the negative and positve signs)

Explanation: r=-2 So,

1st term = 4

2nd term = -8

3rd term= 16

4th term = -32

5th term = 64

6th term = -128

7th term = 256

8th term = -512

9th term = 1024

10th term = -2048

11th term = 4096

12th term= -8192

13th term = 16384

Answer 2

a=4

r = \frac{-16}{4}r=4−16

r = -4r=−4

a_{13} = 4×(-4)^{(13-1)}a13=4×(−4)(13−1)

a_{13} = 4×(-4)^{12}a13=4×(−4)12

a_{13} = 4×16777216a13=4×16777216

a_{13} = 67108864a13=67108864