\(\sqrt{5x-1}+\sqrt[3]{9-x}=2x^2+3x-1\)
Đk:....
\(\Leftrightarrow\sqrt{5x-1}-2+\sqrt[3]{9-x}-2=2x^2+3x-5\)
\(\Leftrightarrow\frac{5x-1-4}{\sqrt{5x-1}+2}+\frac{9-x-8}{\sqrt[3]{9-x}^2+2\sqrt[3]{9-x}+8}=\left(x-1\right)\left(2x+5\right)\)
\(\Leftrightarrow\frac{5\left(x-1\right)}{\sqrt{5x-1}+2}+\frac{-\left(x-1\right)}{\sqrt[3]{9-x}^2+2\sqrt[3]{9-x}+8}-\left(x-1\right)\left(2x+5\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(\frac{5}{\sqrt{5x-1}+2}-\frac{1}{\sqrt[3]{9-x}^2+2\sqrt[3]{9-x}+8}-\left(2x+5\right)\right)=0\)
Dễ thấy: \(\frac{5}{\sqrt{5x-1}+2}-\frac{1}{\sqrt[3]{9-x}^2+2\sqrt[3]{9-x}+8}-\left(2x+5\right)< 0\)
\(\Rightarrow x-1=0\Rightarrow x=1\)
