How can I find the answer for number 1 and 4 with explanation?

Concept: Sequences & Series

The hint here is to try to find the common factor, you asked us to solve 1 so see the solution below.

Next we can find the next 3 terms by just plugging in the values

We want the 6th, 7th, and 8th term

So we plug 6 in for n and 7 in for n and 8 in for n

So we get the 6th term=-243

The 7th term= 729

The 8th term= -2187

Step-by-step explanation:

1) 1 , -3 , 9 , -27 , 81 ,...........

It is Geometric sequence

ratio = 2 term ÷ first term = -3 ÷ 1 = -3

1st term = 1

2nd term = 1 * -3 = -3

3rd term = -3 *(-3) = 9

4th term = 9 *(-3) = - 27

6th term = 81 *(-3) = -243

7th  term = -243 *(-3) =  729

8th term = 729 *(-3) = -2187

Next 3 terms:  - 243 , 729 , - 2187,....

4)

Next 3 terms are : 3/32 , 7/128 , 1/32

41*67/2=1373.5

step-by-step explanation:

i just used a calculator

irrational, cannot