Question

Tìm x : a, \(9.\left(x+1\right)-\left(3x-2\right)=119\) ; b, \(\left(x-3\right)^7=\left(x-3\right)^5\)

Answer 1

a)\(9\left(x+1\right)-\left(3x-2\right)=119\)

\(\Rightarrow9x+9-3x-2=119\)

\(\Rightarrow6x-7=119\Leftrightarrow6x=126\Leftrightarrow x=21\)

b) \(\left(x-3\right)^7=\left(x-3\right)^5\)

\(\Rightarrow\left(x-3\right)^7-\left(x-3\right)^5=0\)

\(\Rightarrow\left(x-3\right)^5\left[\left(x-3\right)^2-1\right]=0\)

\(\Rightarrow\left[{}\begin{matrix}\left(x-3\right)^5=0\\\left(x-3\right)^2=1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x-3=0\\\left[{}\begin{matrix}x-3=1\\x-3=-1\end{matrix}\right.\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=3\\x=4\\x=2\end{matrix}\right.\)