It’s 80 for sure Ik this one
The problem can be solved step by step, if we know certain basic rules of summation. Following rules assume summation limits are identical.




Armed with the above rules, we can split up the summation into simple terms:





=> (a)
f(x)=28n-n^2=> f'(x)=28-2n
=> at f'(x)=0 => x=14
Since f''(x)=-2 <0 therefore f(14) is a maximum
(b)
f(x) is a maximum when n=14
(c)
the maximum value of f(x) is f(14)=196
Answer:

Step-by-step explanation:
So we have the equation:

Add 2 to both sides. The left cancels:

Divide both sides by 6. The left cancels:

So, the value of x is -1.
And we're done!
Since a circle is simple it has no points but it can be folded many times so symmetry is really unlimited for the circle.It is not a plane because it is round and does not have sides.