\(\left\{{}\begin{matrix}3a-2b=27\\6a+8b=26\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}a=\frac{67}{9}\\b=-\frac{7}{3}\end{matrix}\right.\)
b/ ĐKXĐ: ...
\(\sqrt{\frac{1}{x+4}}=4-\sqrt{\frac{5}{x+5}}\)
\(\Leftrightarrow2-\sqrt{\frac{1}{x+4}}+2-\sqrt{\frac{5}{x+5}}=0\)
\(\Leftrightarrow\frac{4-\frac{1}{x+4}}{2+\sqrt{\frac{1}{x+4}}}+\frac{4-\frac{5}{x+5}}{2+\sqrt{\frac{5}{x+5}}}=0\)
\(\Leftrightarrow\frac{4x+15}{\left(x+4\right)\left(2+\sqrt{\frac{1}{x+4}}\right)}+\frac{4x+15}{\left(x+5\right)\left(2+\sqrt{\frac{5}{x+5}}\right)}=0\)
\(\Leftrightarrow4x+15=0\Rightarrow x=-\frac{15}{4}\)
