Question

solve the problem..........​

Answer 1

tn= a+(n-1)d

80=8+(n-1)8

80=8n

Sn=n/2(a+l)

Sn=5(8+80)

Sn=440

Answer 2

Answer:

An+an=80

80-8=72, 80+8=88

8×10=80

n=10

• find S10

An=n/2

S10 =10/2×20

S10=10²-20

S10=80

• THEREFORE THE VALUE OF SUM S10 IS 40