(3x + 3)2 = 144
=> (3x + 3)2 = ( \(\pm\)12)2
=> \(\orbr{\begin{cases}3x+3=12\\3x+3=-12\end{cases}}\Rightarrow\orbr{\begin{cases}3x=9\\3x=-15\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=-5\end{cases}}\)
Bài làm :
(3.x + 3)2 = 144
=> (3.x + 3) = \(\sqrt{144}\)
=> 3.x + 3 = 12
=> 3.x = 12 - 3
=> 3.x = 9
=> x = 9 : 3
=> x = 3
\(\left(3x+3\right)^2=144\)
\(\Leftrightarrow\left(3x+3\right)^2=\left(\pm12\right)^2\)
\(\Leftrightarrow\orbr{\begin{cases}3x+3=12\\3x+3=-12\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}3x=9\\3x=-15\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=-5\end{cases}}\)
