How to write mathematical formulas with Latex in a short time?

Firstly, download a MathType software. [version 6.5 or higher is ok] Secondly, type the formula you need and set Transfer Setttings. See the picture 1.

[  Picture 1: transfer from mathtype to latex settings ]

Thirdly, copy the formula and paste it ino your latex. Remove the content which are framed by red square. Please see picture 2 and 3.

[ Picture 2: copy content from mathtype and paste it into the latex. ]

[ Picture 3: remove some useless content]

Finally, compile the latex and work are done.