欧拉公式：$e^{i\pi}+1=0$

质能方程：$E=mc^2$

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编写公式

When $a \ne 0$, there are two solutions to \\(ax^2 + bx + c = 0\\) and they are
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$

效果如下：
When $a \ne 0$, there are two solutions to \(ax^2 + bx + c = 0\) and they are $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$