2:
a: Khi x=36 thì \(A=\dfrac{6+5}{6-3}=\dfrac{11}{3}\)
b: \(B=\dfrac{\left(\sqrt{x}-2\right)\left(\sqrt{x}+3\right)+\left(\sqrt{x}+1\right)\left(\sqrt{x}-3\right)-x+4\sqrt{x}+9}{x-9}\)
\(=\dfrac{x+\sqrt{x}-6+x-2\sqrt{x}-3-x+4\sqrt{x}+9}{x-9}\)
\(=\dfrac{x+3\sqrt{x}}{x-9}=\dfrac{\sqrt{x}}{\sqrt{x}-3}\)
c: B/A=2
=>\(\dfrac{\sqrt{x}}{\sqrt{x}-3}:\dfrac{\sqrt{x}+5}{\sqrt{x}-3}=2\)
=>\(\dfrac{\sqrt{x}}{\sqrt{x}+5}=2\)
=>2*căn x+10=căn x
=>căn x=-10(loại)
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