a: \(P=\dfrac{\sqrt{x}+5-3}{\sqrt{x}+5}=1-\dfrac{3}{\sqrt{x}+5}\)
căn x+5>=5
=>3/(căn x+5)<=3/5
=>-3/(căn x+5)>=-3/5
=>P>=2/5
Dấu = xảy ra khi x=0
b: \(Q=\dfrac{3\sqrt{x}+6-5}{\sqrt{x}+2}=3-\dfrac{5}{\sqrt{x}+2}\)
căn x+2>=2
=>5/căn x+2<=5/2
=>-5/căn x+2>=-5/2
=>Q>=1/2
Dấu = xảy ra khi x=0
c: \(E=\dfrac{\sqrt{x}+1+5}{\sqrt{x}+1}=1+\dfrac{5}{\sqrt{x}+1}< =1+\dfrac{5}{1}=6\)
Dấu = xảy ra khi x=0
d: \(D=\dfrac{2\sqrt{x}+4+3}{\sqrt{x}+2}=2+\dfrac{3}{\sqrt{x}+2}>=2+\dfrac{3}{2}=\dfrac{7}{2}\)
Dấu = xảy ra khi x=0
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