a: \(A=\left(\dfrac{3}{\sqrt{x}-2}+\dfrac{\sqrt{x}}{\sqrt{x}-2}\right)\cdot\dfrac{1}{\sqrt{x}+3}=\dfrac{1}{\sqrt{x}-2}\)
b: \(\Leftrightarrow x^3-3x+5-x-2=0\)
\(\Leftrightarrow x^3-4x+3=0\)
\(\Leftrightarrow x\left(x-1\right)\left(x+1\right)-3\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x^2+x-3\right)=0\)
\(\Leftrightarrow x\in\left\{1;\dfrac{-1-\sqrt{13}}{2};\dfrac{-1+\sqrt{13}}{2}\right\}\)
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