我正在尝试将以下方程式围绕等号对齐。我该怎么做?谢谢!我正在使用AMSMath包。
$$m\ddot{x}_{1}-K(x_{2}+x_{12})+C(\dot{x}_{12}+\dot{x}_{2})+2C\dot{x}_{1} = fx_{1}$$
$$m\ddot{x}_{2}-K(x_{3}+x_{1})+C(\dot{x}_{1}+\dot{x}_{3})+2C\dot{x}_{2} = fx_{2}$$
$$m\ddot{x}_{3}-K(x_{4}+x_{2})+C(\dot{x}_{2}+\dot{x}_{4})+2C\dot{x}_{3} = fx_{3}$$