markdown语法探究

\[\sum_{i=1}^n a_i=0 \]

\[f(x_1,x_x,\ldots,x_n) = x_1^2 + x_2^2 + \cdots + x_n^2 \]

\[\sum^{j-1}_{k=0}{\widehat{\gamma}_{kj} z_k} \]

\[x^16 \over 12 \]