Question

P= 3✓x -2 / ✓x+7 -2✓x+1/7-√x -4x -✓x +21/x-49 (x≥0 , x khác 49)

Answer 1

\(P=\dfrac{3\sqrt{x}-2}{\sqrt{x}+7}-\dfrac{2\sqrt{x}+1}{7-\sqrt{x}}-\dfrac{4x-\sqrt{x}+21}{x-49}\)

\(=\dfrac{3\sqrt{x}-2}{\sqrt{x}+7}+\dfrac{2\sqrt{x}+1}{\sqrt{x}-7}-\dfrac{4x-\sqrt{x}+21}{\left(\sqrt{x}-7\right)\left(\sqrt{x}+7\right)}\)

\(=\dfrac{\left(3\sqrt{x}-2\right)\left(\sqrt{x}-7\right)+\left(2\sqrt{x}+1\right)\left(\sqrt{x}+7\right)-4x+\sqrt{x}-21}{\left(\sqrt{x}+7\right)\left(\sqrt{x}-7\right)}\)

\(=\dfrac{3x-23\sqrt{x}+14+2x+15\sqrt{x}+7-4x+\sqrt{x}-21}{\left(\sqrt{x}+7\right)\left(\sqrt{x}-7\right)}\)

\(=\dfrac{x-7\sqrt{x}}{\left(\sqrt{x}+7\right)\left(\sqrt{x}-7\right)}=\dfrac{\sqrt{x}}{\sqrt{x}+7}\)