a, (x-15):5+22=24

    ( x - 15 ) : 5 = 2

      x-15  = 10

       x = 25

A) \(\frac{1}{2}\cdot\left(\frac{2}{9}+\frac{3}{7}-\frac{5}{27}\right)\) 

\(=\frac{1}{2}\cdot\frac{1}{2}\)

\(=\frac{1}{4}\)

B)   \(\left(\frac{-5}{28}+1.75+\frac{8}{35}\right):\left(-3\frac{9}{20}\right)\)

\(=\left(\frac{-5}{28}+\frac{7}{4}+\frac{8}{35}\right):\frac{-69}{20}\)

\(=\frac{14}{5}:\frac{-69}{20}\)

\(=\frac{-56}{69}\)

c) Ta có: \(\left\{{}\begin{matrix}\dfrac{x+2}{x+1}+\dfrac{2}{y-2}=6\\\dfrac{5}{x+1}-\dfrac{1}{y-2}=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{x+1}+\dfrac{2}{y-2}=5\\\dfrac{5}{x+1}-\dfrac{1}{y-2}=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{5}{x+1}+\dfrac{10}{y-2}=25\\\dfrac{5}{x+1}-\dfrac{1}{y-2}=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{11}{y-2}=22\\\dfrac{1}{x+1}+\dfrac{2}{y-2}=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y-2=\dfrac{1}{2}\\\dfrac{1}{x+1}=1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x+1=1\\y-2=\dfrac{1}{2}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=0\\y=\dfrac{5}{2}\end{matrix}\right.\)

mình chỉ làm được câu đầu tiên thôi

rồi cậu làm tiếp nhé!!!!!!!!!!!!

=\(\frac{1}{2}.\left(\frac{42}{189}+\frac{81}{189}-\frac{35}{189}\right)\)

các bạn bt làm giúp mình với 

Bài làm:

đkxđ: \(x\ne4;x\ne9\)

Ta có: 

\(P=\frac{2\sqrt{x}}{x-5\sqrt{x}+6}-\frac{\sqrt{x}+3}{\sqrt{x}-2}-\frac{2\sqrt{x}+1}{3-\sqrt{x}}\)

\(P=\frac{2\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}-\frac{\sqrt{x}+3}{\sqrt{x}-2}+\frac{2\sqrt{x}+1}{\sqrt{x}-3}\)

\(P=\frac{2\sqrt{x}-\left(\sqrt{x}+3\right)\left(\sqrt{x}-3\right)+\left(2\sqrt{x}+1\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)

\(P=\frac{2\sqrt{x}-x+9+2x-3\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)

\(P=\frac{x-\sqrt{x}+7}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)

\(ĐKXĐ:4< x< 9\)

\(P=\frac{2\sqrt{x}-9}{x-5\sqrt{x}+6}-\frac{\sqrt{x}+3}{\sqrt{x}-2}-\frac{2\sqrt{x}+1}{3-\sqrt{x}}\)

\(=\frac{2\sqrt{x}-9}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}-\frac{\sqrt{x}+3}{\sqrt{x}-2}+\frac{2\sqrt{x}+1}{\sqrt{x}-3}\)

\(=\frac{2\sqrt{x}-9}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}-\frac{\left(\sqrt{x}+3\right)\left(\sqrt{x}-3\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}+\frac{\left(2\sqrt{x}+1\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)

\(=\frac{\left(2\sqrt{x}-9\right)-\left(\sqrt{x}+3\right)\left(\sqrt{x}-3\right)+\left(2\sqrt{x}+1\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)

\(=\frac{2\sqrt{x}-9-x+9+2x-3\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}=\frac{x-\sqrt{x}-2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}\)

\(=\frac{\left(\sqrt{x}-2\right)\left(\sqrt{x}+1\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-3\right)}=\frac{\sqrt{x}+1}{\sqrt{x}-3}\)

\(\Leftrightarrow\left(\frac{3}{4}x-\frac{9}{16}\right)\left(\frac{1}{3}-\frac{3}{5}.\frac{1}{x}\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}\frac{3}{4}x-\frac{9}{16}=0\\\frac{1}{3}-\frac{3}{5}.\frac{1}{x}=0\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=\frac{3}{4}\\x=\frac{9}{5}\end{cases}}\)

Vậy \(x\in\left\{\frac{3}{4};\frac{9}{5}\right\}\)

Ta có: \(B=\frac{\sqrt{\frac{1}{9}}-3}{\sqrt{\frac{1}{9}}-1}\)

\(B=\frac{\frac{1}{3}-3}{\frac{1}{3}-1}\)

\(B=\frac{-\frac{8}{3}}{-\frac{2}{3}}=4\)

đkxđ: \(\hept{\begin{cases}x\ne1\\x\ne25\end{cases}}\)

Ta có:  

\(A=\frac{x-21}{x-6\sqrt{x}+5}+\frac{1}{\sqrt{x}-1}+\frac{1}{5-\sqrt{x}}\)

\(A=\frac{x-21}{\left(\sqrt{x}-1\right)\left(\sqrt{x}-5\right)}+\frac{1}{\sqrt{x}-1}-\frac{1}{\sqrt{x}-5}\)

\(A=\frac{x-21+\sqrt{x}-5-\sqrt{x}+1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}-5\right)}\)

\(A=\frac{x-25}{\left(\sqrt{x}-1\right)\left(\sqrt{x}-5\right)}\)

\(A=\frac{\left(\sqrt{x}-5\right)\left(\sqrt{x}+5\right)}{\left(\sqrt{x}-1\right)\left(\sqrt{x}-5\right)}\)

\(A=\frac{\sqrt{x}+5}{\sqrt{x}-1}\)

\(\frac{9620}{979}\)