a: \(P=\left(\frac{\sqrt{a}+1}{\sqrt{a}-1}-\frac{\sqrt{a}-1}{\sqrt{a}+1}+4\sqrt{a}\right)\cdot\frac{1}{2a\cdot\sqrt{a}}\)
\(=\left(\frac{\left(\sqrt{a}+1\right)^2-\left(\sqrt{a}-1\right)^2}{a-1}+4\sqrt{a}\right)\cdot\frac{1}{2a\cdot\sqrt{a}}\)
\(=\left(\frac{a+2\sqrt{a}+1-a+2\sqrt{a}-1}{a-1}+4\sqrt{a}\right)\cdot\frac{1}{2a\cdot\sqrt{a}}=4\sqrt{a}\left(\frac{1}{a-1}+1\right)\cdot\frac{1}{2a\cdot\sqrt{a}}\)
\(=\frac{2}{a}\cdot\frac{1+a-1}{a-1}=\frac{2}{a-1}\)
b: P=a
=>a(a-1)=2
=>\(a^2-a-2=0\)
=>(a-2)(a+1)=0
=>a=2(nhận) hoặc a=-1(loại)
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