a: ĐKXĐ: \(a\notin\left\{0;1;-1\right\}\)
Sửa đề: \(E=\left(\dfrac{a+1}{a-1}-\dfrac{a-1}{a+1}+4a\right)\cdot\dfrac{1}{2a^3}\)
\(E=\dfrac{a^2+2a+1-a^2+2a-1+4a\left(a^2-1\right)}{a^2-1}\cdot\dfrac{1}{2a^3}\)
\(=\dfrac{4a+4a\left(a^2-1\right)}{a^2-1}\cdot\dfrac{1}{2a^3}\)
\(=\dfrac{4a\left(a^2-1+1\right)}{a^2-1}\cdot\dfrac{1}{2a^3}\)
\(=\dfrac{2}{a^2-1}\)
b: Để E=a thì \(a^3-a-2=0\)
=>\(a\in\left\{1.52\right\}\)
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