a)
x=(2^{-3})^{-2}=2^{-3*(-2)}=2^6=64
y=(2\sqrt5+2)^{\frac{1}{2}}*(2\sqrt5-2)^{\frac{1}{2}}=\sqrt{2\sqrt5+2}*\sqrt{2\sqrt5-2}=
=\sqrt{(2\sqrt5+2)(2\sqrt5-2)}=\sqrt{(2\sqrt5)^2-2^2}=\sqrt{4*5-4}=\sqrt{16}=4
x>y
b)
x=3^{\frac{1}{2}}*12^{-0,5}=3^{\frac{1}{2}}*12^{-\frac{1}{2}}=3^{\frac{1}{2}}*(\frac{1}{12})^{\frac{1}{2}}=\sqrt3*\sqrt{\frac{1}{12}}=\sqrt{\not3^1*\frac{1}{\not12^4}}=\sqrt{\frac{1}{4}}=\frac{1}{2}
y=9^{-0,75}*9^{\frac{1}{4}}*81^{\frac{3}{4}}=9^{-\frac{3}{4}}*9^{\frac{1}{4}}*(9^2)^{\frac{3}{4}}==9^{-\frac{3}{4}+\frac{1}{4}+\frac{6}{4}}=9^{\frac{4}{4}}=9^1=9
y>x