egin{align} & frac{{ - b pm sqrt {{b^2} - 4ac} }}{{2a}} \\ & frac{{sqrt {{c^2} - {d^2}} }}{{3a}} end{align}
显示如下
egin{align} & frac{{ - b pm sqrt {{b^2} - 4ac} }}{{2a}} \ & frac{{sqrt {{c^2} - {d^2}} }}{{3a}} end{align}