测试

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}