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Giải thích các bước giải:

a.Ta có:

$A=2\sqrt8-\sqrt{50}+\sqrt{(\sqrt2-1)^2}$

$\to A=2\cdot 2\sqrt2-5\sqrt2+\sqrt2-1$

$\to A=4\sqrt2-5\sqrt2+\sqrt2-1$

$\to A=-1$

b.Tac ó:

$B=(\dfrac1{\sqrt{x}+1}+\dfrac1{\sqrt{x}-1}):\dfrac{\sqrt{x}}{x-1}$

$\to B=\dfrac{\sqrt{x}-1+\sqrt{x}+1}{(\sqrt{x}+1)(\sqrt{x}-1)}\cdot\dfrac{x-1}{\sqrt{x}}$

$\to B=\dfrac{2\sqrt{x}}{x-1}\cdot \dfrac{x-1}{\sqrt{x}}$

$\to B=2$

c.Để $(P)$ đi qua $A(2, 4)$

$\to 4=a\cdot 2^2$

$\to a=1$