giúp toooooo vớiiiiii

a, khi x=16 thì

A=$\frac{16+3}{4-2}$ =$\frac{19}{2}$ 

b, B=$\frac{x+5\sqrt{x}+6-3\sqrt{x}-6}{(\sqrt{x}+2)(\sqrt{x}-2)}$ 

B=$\frac{\sqrt{x}(\sqrt{x}+2)}{(\sqrt{x}+2)(\sqrt{x}-2)}$ 

B= $\frac{\sqrt{x}}{\sqrt{x}-2}$ 

c, A:B 

$\frac{x+3}{\sqrt{x}-2}$ . $\frac{\sqrt{x}-2}{\sqrt{x}}$ 

= $\frac{x+3}{\sqrt{x}}$ 

$\frac{x+3}{\sqrt{x}}$ -3

= $\frac{x+3-3\sqrt{x}}{\sqrt{x}}$ <0

Vậy A:B<3