Question

10.The sum of first 16 terms of the AP: 10, 6 ,2, ....is

− 320− 320

320320

640640

 − 352 − 352


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Answer 1

- 320

Explanation:

a₁ = 10

a₂ = 6

d = a₂ - a₁ = 6 - 10 = -4

n = 16

a₁₆ = a₁ + (n-1)•d = 10 + (16-1)•(-4) = 10 - 60 = -50

`S_(n)=(a_1+a_n)/(2)\cdot n\\\\\\S_(16)=(10-50)/(2)\cdot 16=-40\cdot8=-320`