## anonymous one year ago WILL GIVE MEDAL!! Find an explicit rule for the nth term of the sequence. 2, -8, 32, -128, ... @ganeshie8 @Luigi0210 @whpalmer4

1. freckles

hint: think geometric sequence

2. freckles

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

3. freckles

can you find the common ratio ?

4. anonymous

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

5. freckles

so yes the common ratio is -4 notice your first term is 2 the geometric series in explicit form looks like: $a_n=a_1 \cdot r^{n-1}$

6. freckles

a_1=2 and r=-4

7. anonymous

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

8. freckles

yep

9. anonymous

Thank you!