Answer:
aₙ = -15 + 10 * (n-1)
Step-by-step explanation:
aₙ = a₁ + (n-1)*d a₁: first term d: common difference
a₅ a₁ + 4d =25 .... (1)
a₁₁ a₁ + 10d = 85 ...(2)
(2) - (1) 6d = 60
d = 10
a₁ = -15
Formula: aₙ = -15 + 10 * (n-1)
angle BOD = angle AOC
( cuz they are vertical opposite angles )
so angle BOD = 65°
Just took it!
See the attached picture:
