a/ \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\)
\(x.\left(-\frac{1}{6}\right)=\frac{7}{12}\)
\(x=\frac{7}{12}:\left(-\frac{1}{6}\right)\)
\(x=\frac{7}{12}.\left(-6\right)=-\frac{7}{2}\)
b/ \(\left(x+3\right)^2=\frac{9}{25}\)
\(\left(x+3\right)^2=\left(\frac{3}{5}\right)^2\)
\(\Rightarrow x+3=\frac{3}{5}\)
\(x=\frac{3}{5}-3=\frac{3}{5}-\frac{15}{5}=-\frac{12}{5}\)
a, \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\)
\(x\left(-\frac{1}{6}\right)=\frac{7}{12}\)
\(x=\frac{7}{12}:\left(-\frac{1}{6}\right)\)
\(x=-\frac{7}{2}\)
b, \(\left(x+3\right)^2=\frac{9}{25}\)
\(\left(x+3\right)^2=\left(\frac{3}{5}\right)^2\)
\(x+3=\frac{3}{5}\)
\(x=\frac{3}{5}-3\)
\(x=-\frac{12}{5}\)
a) \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
⇒ \(\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
⇒ \(-\frac{1}{6}x=\frac{7}{12}\)
⇒ \(x=\frac{7}{12}:\left(-\frac{1}{6}\right)\)
⇒ \(x=-\frac{7}{2}\)
Vậy \(x=-\frac{7}{2}.\)
b) \(\left(x+3\right)^2=\frac{9}{25}\)
⇒ \(x+3=\pm\frac{3}{5}\)
⇒ \(\left[{}\begin{matrix}x+3=\frac{3}{5}\\x+3=-\frac{3}{5}\end{matrix}\right.\) ⇒ \(\left[{}\begin{matrix}x=\frac{3}{5}-3\\x=\left(-\frac{3}{5}\right)-3\end{matrix}\right.\) ⇒ \(\left[{}\begin{matrix}x=-\frac{12}{5}\\x=-\frac{18}{5}\end{matrix}\right.\)
Vậy \(x\in\left\{-\frac{12}{5};-\frac{18}{5}\right\}.\)
c) \(7^{x+2}+2=345\)
⇒ \(7^{x+2}=345-2\)
⇒ \(7^{x+2}=343\)
⇒ \(7^{x+2}=7^3\)
⇒ \(x+2=3\)
⇒ \(x=3-2\)
⇒ \(x=1\)
Vậy \(x=1.\)
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