The explicit formula for given sequence is: 
Step-by-step explanation:
Given sequence is:
-1,4,-16,64.....
We can see that there is no same difference between consecutive terms so we will find common ratio to see if it is a geometric sequence.
Here

The explicit formula for geometric sequence is:

Putting the values of r and a1

Hence
The explicit formula for given sequence is: 
Keywords: Geometric sequence, common ratio
Learn more about geometric sequence at:
#learnwithBrainly
Answer: 9−27
Step-by-step explanation:
Answer:
x = -2
Step-by-step explanation:
<u><em>First, you need to subtract 8x from both sides:</em></u>
8x – 4 = 13x + 6
-8x -8x
____________
-4 = 5x + 6
<em><u>Then, subtract 6 from both sides:</u></em>
-4 = 5x + 6
-6 - 6
________
-10 = 5x
<u><em>Lastly, divide both sides by 5:</em></u>
-10 = 5x
-2 = x
I don’t really know exactly what you’re asking but if you’re asking what is most practical, it would be #4