Question

What is the 20th term of the sequence that begins -2, 4, -8, 16...?

Answer 1

options are
a. 2,097,152
b. 524,288
c. -524,288
d. 1,048,576

Answer 2

please explain or show how to get answer?

Answer 3

this is a geometric sequence since each term is -2 times the previous term. This is the formula for a geometric sequence
\[a_n=a_1r^{n-1}\]

r = the common ratio (what you're multiplying by)
a_1 = first term = -2

So the equation for your sequence is \[a_n=-2(-2)^{n-1}\]

Then you'd plug in 20 for n to find the 20th term

Answer 4

so a(20)=-2(-2)^20-1? how do you evaluate the rest?

Answer 5

stick that in a calculator.

Answer 6

i got 1,048,576. so d is correct?

Answer 7

thank you :)