a) \(\sqrt{98}-\sqrt{72}+0,5\sqrt{8}=7\sqrt{2}-6\sqrt{2}+\sqrt{2}=2\sqrt{2}\)
b) \(\left(2\sqrt{3}+\sqrt{5}\right).\sqrt{3}-\sqrt{60}=6+\sqrt{15}-2\sqrt{15}=6-\sqrt{15}\)
c) \(\left(\sqrt{x}+2\right)\left(x-2\sqrt{x}+4\right)=\left(\sqrt{x}\right)^3+8\)
d) \(\left(\sqrt{x}-\sqrt{y}\right)\left(x+y+\sqrt{xy}\right)=\left(\sqrt{x}\right)^3-\left(\sqrt{y}\right)^3\)