1. (8*100^n) / (2^ (2*n+1) * 5^ (2*n-2))

2. (5^ (n+1) - 5^ (n-1)) / (2*5^n)

3. (a-sqrt (a) - 2) / (2-sqrt (a))

8*100^n/2^n+1 * 5^n-2=2³*2^2n*5^2n/2^n+1 * 5^n-2=2^2n+3*5^2n/2^n+1 * 5^n-2=

=2²*5²=10²=100

2) (5^n+1 - 5^n-1) / 2*5^n=5^n-1 * (25-1) / 2*5^n=5^n-1 * 24/2*5^n=12/5=2,4

3) (a-√a-2) / (2-√a) = (a-√a-2) (2+√a) / (2-√a) (2+√a) = (2a+a√a-2√a-a-4-2√a) / (4-a) =

(a+a√a-4√a-4) / (4-a) = [a (1+√a) - 4 (√a+1) ] / (4-a) = (a-4) (1+√a) / (4-a) = - 1-√a