16. Tính a.A= \(\frac{\sqrt{2-\sqrt{4x-x^2}}}{x-2}\) (x>2; \(\sqrt{x}+\sqrt{4+x}=a\); a là hằng số)
b.B=\(\frac{\sqrt{6+2\sqrt{9-4x^2}}}{x}\)( IxI\(\le\)\(\frac{3}{2}\); \(x\ne0;\sqrt{3+2x}-\sqrt{3-2x}=a\); a là hằng số)
c. \(C=x^2+\sqrt{x^4+x+1}\left(x=\frac{1}{2}.\sqrt{\sqrt{2}+\frac{1}{8}}-\frac{\sqrt{2}}{8}\right)\)