Write the explicit formula that represents the geometric sequence -2, 8, -32, 128

Question

nnesha · Answer

$$\huge\rm a_n = a_1 \times r^{n-1}$$
formula to find geometric sequence
where a1 is first term
r is ratio
and  n = next term
now replace variables by their valeus

usukidoll · Answer

looks like we're alternating signs and exponent numbers

usukidoll · Answer

hmm...
(-1)^n-1[2]^n-1

usukidoll · Answer

would work if those even numbers would buzz

(-1)^2n-1 [2]^2n-1

usukidoll · Answer

yup that fixed it

usukidoll · Answer

give meh medalz ^_^

nnesha · Answer

(-1)^2n-1 [2]^2n-1
???

usukidoll · Answer

$$(-1)^{2n-1}2^{2n-1}$$

usukidoll · Answer

now plug in n = 1 2 3 .. you will get only odd number results and alternating signs

usukidoll · Answer

oh geez I thought it was find the series.. -_-

nnesha · Answer

@bbrown1759 <---this person asked this question
he/she is not here

nnesha · Answer

@bbrown1859
"geometric sequence" that is a geometric sequence 
so try to find the number which u multiply by -2 and get positive 8
that number is going to be ratio =r

anonymous · Answer

Ty @Nnesha I figured it out after you send me the formula. And thank you @Usukidoll for your help.

nnesha · Answer

np :)