`$\text{a, Thay x = 16 (tm) vào B}$
`⇒B=1-\frac{\sqrt{16}-3}{\sqrt{16}-2}=1-1/2=1/2`
$\text{Vậy tại x = 16 thì B = $\dfrac{1}{2}$}$
`b,C=A:B`
`⇒C=(\frac{x+2}{x-\sqrt{x}-2}-\frac{2\sqrt{x}}{\sqrt{x}+1}-\frac{1-\sqrt{x}}{\sqrt{x}-2}):(1-\frac{\sqrt{x}-3}{\sqrt{x}-2})` `(x ≥ 0; x ne 4)`
`C=\frac{x+2-2\sqrt{x}(\sqrt{x}-2)-(1-\sqrt{x})(\sqrt{x}+1)}{(\sqrt{x}+1)(\sqrt{x}-2)}:\frac{\sqrt{x}-2-\sqrt{x}+3}{\sqrt{x}-2}`
`C=\frac{x+2-2x+4\sqrt{x}-1+x}{(\sqrt{x}+1)(\sqrt{x}-2)}.(\sqrt{x}-2)`
`C=\frac{4\sqrt{x}+1}{\sqrt{x}+1}`
$\text{c, Để C dương}$
`⇔ \frac{4\sqrt{x}+1}{\sqrt{x}+1} > 0`
$\text{Có: 4$\sqrt{x}$ +1 > 0 ∀ x; $\sqrt{x}$ + 1 > 0 ∀ x}$
`⇒BT > 0 ∀ x`
