Answer:
An=9+2(n-1)
Step-by-step explanation:
Just learned this.
Its a arithmetic so it would always be a n-1 however it would be in parentheses after the common different.
Because it is easily divisible by 2, 3, 4, 6, 8, 12 and itself
The percentage error is 10%
A=(pie)r2 is the formula for a circle