Answer: I think it’s A if I am incorrect I am very sorry
Step-by-step explanation:
Answer:
For First Solution: 
is the solution of equation y''-y=0.
For 2nd Solution:
is the solution of equation y''-y=0.
Step-by-step explanation:
For First Solution: 
In order to prove whether it is a solution or not we have to put it into the equation and check. For this we have to take derivatives.

First order derivative:

2nd order Derivative:

Put Them in equation y''-y=0
e^t-e^t=0
0=0
Hence
is the solution of equation y''-y=0.
For 2nd Solution:

In order to prove whether it is a solution or not we have to put it into the equation and check. For this we have to take derivatives.

First order derivative:

2nd order Derivative:

Put Them in equation y''-y=0
cosht-cosht=0
0=0
Hence
is the solution of equation y''-y=0.
The next three terms of -243, 81, -27, 9 is
The given series is geometric series
<u>Solution:</u>
Given, series is -243, 81, -27, 9, …
We have to find the next three terms of the above given series.
Now, the given series can also be written as

We can say that, above series is in Geometric Progression with first term = -243 and common ratio = 
Then, next three term would be,

Hence, the next three terms of given G.P series are
The sum of 5+2 or 2+5 is 7. It's the same because it doesn't matter if the equation is flipped around in addition.