Tìm x , biết :a) (frac{{ – ,11}}{{12}},.

Câu hỏi:

Tìm x , biết :

a) \(\frac{{ – \,11}}{{12}}\,.\,\user2{x}\, + \,0,25\, = \,\frac{5}{6}\)                     

Bạn đang xem: Tìm x , biết :a) (frac{{ – ,11}}{{12}},.

b) \({\left( {\user2{x} – 1} \right)^5} =  – 32\)

a) \(\frac{{ – \,11}}{{12}}\,.\,\user2{x}\, + \,0,25\, = \,\frac{5}{6}\)           

          \(\begin{array}{l}
\frac{{ – \,11}}{{12}}\,.\,\user2{x}\, + \,\frac{1}{4}\, = \,\frac{5}{6}\\
\frac{{ – \,11}}{{12}}\,.\,\user2{x} = \frac{5}{6} – \frac{1}{4}\\
\frac{{ – \,11}}{{12}}\,.\,\user2{x} = \frac{7}{{12}}\\
x = \frac{{ – 7}}{{11}}
\end{array}\)

b) \({\left( {\user2{x} – 1} \right)^5} =  – 32\)

Ta có \({\left( {\user2{x}\, – \,1} \right)^5}\, = \,{\left( { – \,2} \right)^5}\)

\( \Rightarrow \,\,\user2{x}\, – \,1\, = \, – \,2\,\,\,\, \Rightarrow \,\,\,\,x\,\, = \,\, – \,1\)