Question

Write the explicit formula for the geometric sequence
a1 = -5 a2 = 20 a3 = -80

I already picked "A" so i'm not including it
I think the right answer is D but i am not certain.

B. an = -5(-4)n-1

C. an = -4(-5)n-1

D. an = -5 • (4)n

Answer 1

the formula for the nth term

an = a1r^(n-1)

where a1 = first term and r = common ratio

common ratio ra = second term / first term = 20/-5 = ?

D is not correct

Answer 2

4?

Answer 3

@welshfella

Answer 4

common ratio r = 20/-5 = -4


( + / - = -)

Answer 5

So it would be B.

Answer 6

yes

Answer 7

Alright thanks

Answer 8

yw