The only formula that can be used to describe the sequence is definitely the third one

. So count like that

and so on. You can check others by yourself to check if I'm right or not.
the sign would probably be a negative. imagine this - - - - - - and then + + +, cancel out the negatives and plus then you are left with more negatives than positive so the sign will take the negative sign.
Answer:
A
Step-by-step explanation:
Answer:
x=-0.5
Step-by-step explanation:
the question is -9=18x
we divide both sides by 9
-1=2x
divide both sides by 2
x=-0.5