Question

WILL GIVE MEDAL!!
Find an explicit rule for the nth term of the sequence.

2, -8, 32, -128, ...

@ganeshie8 @Luigi0210 @whpalmer4

Answer 1

hint: think geometric sequence

Answer 2

In case you have no memory of what that means
it means term divided by previous term will always be equal to the same number
we call this number the common ratio

Answer 3

can you find the common ratio ?

Answer 4

Each number is multiplied by -4 to get to the next number

Answer 5

so yes the common ratio is -4
notice your first term is 2

the geometric series in explicit form looks like:
\[a_n=a_1 \cdot r^{n-1}\]

Answer 6

a_1=2 and r=-4

Answer 7

an= 2*(-4)^(n-1)?

Answer 8

yep

Answer 9

Thank you!