a, rút gọn
\(A=\dfrac{2\sqrt{a}-9}{a-5\sqrt{a}+6}-\dfrac{\sqrt{a}+3}{\sqrt{a}-2}-\dfrac{2\sqrt{a}+1}{3-\sqrt{a}}\)
\(A=\dfrac{2\sqrt{a}-9}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}-\dfrac{\sqrt{a}+3}{\sqrt{a}-2}+\dfrac{2\sqrt{a}+1}{\sqrt{a}-3}\)
\(A=\dfrac{2\sqrt{a}-9}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}-\dfrac{\left(\sqrt{a}+3\right)\left(\sqrt{a}-3\right)}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}+\dfrac{\left(2\sqrt{a}+1\right)\left(\sqrt{a}-2\right)}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}\)
\(A=\dfrac{2\sqrt{a}-9-\left(\sqrt{a}\right)^2+3^2+2a-4\sqrt{a}+\sqrt{a}-2}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}\)
\(A=\dfrac{2\sqrt{a}-9-a+9+2a-4\sqrt{a}+\sqrt{a}-2}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}\)
\(A=\dfrac{a-\sqrt{a}-2}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}\)
\(A=\dfrac{a+\sqrt{a}-2\sqrt{a}-2}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}\)
\(A=\dfrac{\left(\sqrt{a}-2\right)\left(\sqrt{a}+1\right)}{\left(\sqrt{a}-2\right)\left(\sqrt{a}-3\right)}\)
\(A=\dfrac{\sqrt{a}+1}{\sqrt{a}-3}\)