\(\left(\frac{1}{x+2\sqrt{x}}-\frac{1}{\sqrt{x}+2}\right):\frac{1-\sqrt{x}}{x+4\sqrt{x}+4}\)
a) Rút gọn A
b)Tìm x để \(F=\frac{5}{2}\)
Đừng làm tắt nghen :>
K
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23 tháng 6 2021
\(ĐKXĐ:x\ge0;x\ne1;0\)
\(A=\frac{2x+2}{\sqrt{x}}+\frac{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}{\sqrt{x}\left(\sqrt{x}-1\right)}-\frac{\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)}{\sqrt{x}\left(\sqrt{x}+1\right)}\)
\(A=\frac{2x+2}{\sqrt{x}}+\frac{x+\sqrt{x}+1}{\sqrt{x}}-\frac{x-\sqrt{x}+1}{\sqrt{x}}\)
\(A=\frac{2x+2+x+\sqrt{x}+1-x+\sqrt{x}-1}{\sqrt{x}}\)
\(A=\frac{2x+2+2\sqrt{x}}{\sqrt{x}}\)
\(A=2\sqrt{x}+\frac{2}{\sqrt{x}}+2\)
a/d bđt cauchy
\(2\sqrt{x}+\frac{2}{\sqrt{x}}\ge2\sqrt{2.2}=2.2=4\)
\(A\ge4+2=6\)
\(< =>A>5\)
dấu "=" xảy ra khi x=1
5 tháng 2 2022
a: \(A=\dfrac{\left(\sqrt{a}-\sqrt{b}\right)^2}{\sqrt{a}-\sqrt{b}}-\dfrac{\sqrt{ab}\left(\sqrt{a}+\sqrt{b}\right)}{\sqrt{ab}}\)
\(=\sqrt{a}-\sqrt{b}-\sqrt{a}-\sqrt{b}=-2\sqrt{b}\)
b: \(B=\dfrac{2\sqrt{x}-x-x-\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\cdot\dfrac{x+\sqrt{x}+1}{x-1}\)
\(=\dfrac{-2x+\sqrt{x}-1}{\sqrt{x}-1}\cdot\dfrac{1}{x-1}\)
c: \(C=\dfrac{x-9-x+3\sqrt{x}}{x-9}:\left(\dfrac{3-\sqrt{x}}{\sqrt{x}-2}+\dfrac{\sqrt{x}-2}{\sqrt{x}+3}+\dfrac{x-9}{x+\sqrt{x}-6}\right)\)
\(=\dfrac{3\left(\sqrt{x}-3\right)}{x-9}:\dfrac{9-x+x-4\sqrt{x}+4+x-9}{\left(\sqrt{x}+3\right)\left(\sqrt{x}-2\right)}\)
\(=\dfrac{3}{\sqrt{x}+3}\cdot\dfrac{\left(\sqrt{x}+3\right)\left(\sqrt{x}-2\right)}{x-4\sqrt{x}+4}\)
\(=\dfrac{3}{\sqrt{x}-2}\)
KH
11 tháng 2 2020
\(1,ĐKXĐ:x\ge0;x\ne4\)
\(A=\left(1+\frac{2}{\sqrt{x}}\right)\left(\frac{\sqrt{x}-2+\sqrt{x}+2-4}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\right)\)
\(A=\left(1+\frac{2}{\sqrt{x}}\right)\left(\frac{2\sqrt{x}-4}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\right)\)
\(A=\left(1+\frac{2}{\sqrt{x}}\right)\left(\frac{2\left(\sqrt{x}-2\right)}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\right)\)
\(A=\left(\frac{\sqrt{x}+2}{\sqrt{x}}\right)\left(\frac{2}{\sqrt{x}+2}\right)\)
\(A=\frac{2}{\sqrt{x}}\)
\(2,A>\frac{1}{2}\)
\(\Leftrightarrow\frac{2}{\sqrt{x}}>\frac{1}{2}\)
\(\Leftrightarrow\frac{2}{\sqrt{x}}-\frac{1}{2}>0\)
\(\Leftrightarrow\frac{4}{2\sqrt{x}}-\frac{\sqrt{x}}{2\sqrt{x}}>0\)
\(\Leftrightarrow\frac{4-\sqrt{x}}{2\sqrt{x}}>0\)
Do \(\sqrt{x}>0\Rightarrow2\sqrt{x}>0\)
\(\Rightarrow4-\sqrt{x}>0\)
\(\Leftrightarrow-\sqrt{x}>-4\)
\(\Leftrightarrow\sqrt{x}< 4\)
\(\Leftrightarrow x< 16\)
Kết hợp với ĐKXĐ thì \(0\le x< 16\)và \(x\ne4\)
\(3,A=-2\sqrt{x}+5\)
\(\Leftrightarrow\frac{2}{\sqrt{x}}=-2\sqrt{x}+5\)
\(\Leftrightarrow\sqrt{x}\left(-2\sqrt{x}+5\right)=2\)
\(\Leftrightarrow-2x+5\sqrt{x}-2=0\)
\(\Leftrightarrow-2x+2.5\sqrt{x}+2.5\sqrt{x}-2=0\)
\(\Leftrightarrow\left(-2x+2.5\sqrt{x}\right)+\left(2.5\sqrt{x}-2\right)=0\)
Đến đây thì mình chịu
Bạn tự giải nốt nhé
HỌC TỐT
30 tháng 1 2022
a: \(Q=\dfrac{4\sqrt{x}\left(\sqrt{x}-2\right)-8x}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}:\dfrac{\sqrt{x}-1-2\left(\sqrt{x}-2\right)}{\sqrt{x}\left(\sqrt{x}-2\right)}\)
\(=\dfrac{-8\sqrt{x}}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\cdot\dfrac{\sqrt{x}\left(\sqrt{x}-2\right)}{\sqrt{x}-1-2\sqrt{x}+4}\)
\(=\dfrac{-8x}{\sqrt{x}+2}\cdot\dfrac{1}{3-\sqrt{x}}=\dfrac{8x}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-3\right)}\)
b: Để Q=-1 thì \(8x=-\left(\sqrt{x}+2\right)\left(\sqrt{x}-3\right)\)
\(\Leftrightarrow8x+x-\sqrt{x}-6=0\)
\(\Leftrightarrow9x-\sqrt{x}-6=0\)
Bạn xem lại đề, nghiệm này rất xấu
a, \(\left(\frac{1}{x+2\sqrt{x}}-\frac{1}{\sqrt{x}+2}\right):\frac{1-\sqrt{x}}{x+4\sqrt{x}+4}\)ĐK : x >= 0 ; \(x\ne1\)
\(=\left(\frac{1-\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+2\right)}\right).\frac{\left(\sqrt{x}+2\right)^2}{1-\sqrt{x}}=\frac{\sqrt{x}+2}{\sqrt{x}}\)
b, \(F=\frac{5}{2}\Rightarrow\frac{\sqrt{x}+2}{\sqrt{x}}=\frac{5}{2}\Rightarrow2\sqrt{x}+4=5\sqrt{x}\Leftrightarrow3\sqrt{x}=4\Leftrightarrow x=\frac{16}{9}\)
ĐK : x > 0 , x khác 1
\(bthuc=\frac{1-\sqrt{x}}{\sqrt{x}\left(\sqrt{x}+2\right)}\cdot\frac{\left(\sqrt{x}+2\right)^2}{1-\sqrt{x}}=\frac{\sqrt{x}+2}{\sqrt{x}}\)
Để bthuc = 5/2 thì \(\frac{\sqrt{x}+2}{\sqrt{x}}=\frac{5}{2}\Rightarrow2\sqrt{x}+4=5\sqrt{x}\Leftrightarrow3\sqrt{x}=4\Leftrightarrow x=\frac{16}{9}\left(tm\right)\)