Question

PLEASE ANSWER THIS : 40 POINTS

Answer 1

the answer is -50 if you would like the work pls contact me personally

Answer 2

Answer:

S10 = -50

Step-by-step explanation:

an = a1 +d(n-1) is the formula for an arithmetic series

The 4th term is

4  =a1 + d(4-1)

4 = a1 + 3d

The 8th term is

-20  =a1 + d(8-1)

-20 = a1 + 7d

Subtract these two equations

-20 = a1 + 7d

-(4 = a1 + 3d)

--------------------------

Distribute the subtraction sign

-20 = a1 + 7d

-4 =- a1 - 3d

--------------------------

-24 = 4d

Divide by 4

-24/4 = 4d/4

-6 =d

Now we can calculate a1

4 = a1 + 3d

4 = a1 +3(-6)

4 = a1 -18

Add 18 to each side

4+18 =a1

a1 =22

an = 22 -6(n-1)

The sum is found by using

Sn = n/2 (a1+an)

We need the 10th term

a10 =  22 -6(10-1)

a10 = 22 -6*9

       =22 -54

         =-32

Sn = 10/2 (22-32)

     = 5(-10)

    -50