normal equation的用法和樣例：
例句
- The method of undetermined coefficients is the general method of solving a linear differential equation with constant coefficients of the second order.
摘要二階常係數線性微分方程可用常規方法待定係數法求解。 - One side of an equation must balance the other.
方程式的一邊必須和另一邊相等。 - Show me how to solve this equation.
告訴我，這個方程式怎麼解。
