Step-by-step explanation:
Sn=n/2(2a+(n-1)d)
910=n/2{2a+(n-1)d}
1820=n{2a+(n-1)d}
1820=20{2a+(20-1)d}
1820=20{2a+19d}
91=2a+19d
An=a+(n-1)d
95=a+(20-1)d
95=a+19d
91=2a+19d
---------------
4=-a
a=-4
91=2a+19d
91=2(-4)+19d
91=-8+19d
91+8=19d
99=19d
d=99/19
A=-4
Yes 8.54 as rational number because in can be written as 854/100
Answer:

Step-by-step explanation:
Use the circle equation, 
Plug in the center and radius:

Simplify:

So, the equation is 
5 - 1 2/9 = 3 7/9
Hope this helps!
For this, let's have:
n represent each number, the number after it is its place in sequence
/ means divide
n1 /2 = n2, etc.