Tridifferential and infinite series are necessary and inevitable for postgraduate entrance examination. If you give up, it may be over 90, but there are still more than 20 days. This part should be able to make up. The main work should be to collect the problems of three differential and infinite series over the years and practice them in a targeted way. In fact, the questions are basically fixed every year, so as long as you grasp this question well and practice well, it should be no problem. I wish you success, come on, do you still care about these 20 days after so many days? Sit on the bench and win is yours.