Answer:
[tex]\boxed{\bf x_1=3; \quad x_2=-3}[/tex]
Step-by-step explanation:
[tex]\displaystyle \tt 4x^2=36\quad \leftrightarrow\quad x^2=9\quad \leftrightarrow \quad x=\pm\sqrt{9} \quad \leftrightarrow \quad \boxed{\bf x_1=3;\quad x_2=-3}[/tex]
