Answer:
+2x+15
Step-by-step explanation:
-3x+5x=+2x
(+2x-7) × (+8)
(+2x)(+15)
I THINK
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:
They are in A. P so the sum will be 2380