Question

50PTS and brainliest! PLEASE HURRY!

Answer 1

An=−11+(n−1)⋅6, n is the number of terms

Answer 2

1) F + (N - 1)*D=Nth Term, where F=First term, D=Common difference and N=Number of terms.

-1 + (8 - 1)*D =20, solve for D

-1 + 7D = 20

7D = 20 + 1

7D =21 divide both sides by 7

D = 21 / 7

D = 3 Common difference

 

2)

(F + L) / 2*N, where F=First term, L=Last term and N=Number of terms.

Sum = (-7 - 115) / 2*13

Sum =( -122 / 2) * 13

Sum = -61 * 13

Sum = -793