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 ]