# Composition of Differential Operators

## Question

For example, I have to write down the differential operator below as a polynomial in $\partial$ $$(\partial-f_n(x))(\partial-f_{n-1}(x))\cdots(\partial-f_1(x))$$where the product means composition.

# Quiz 6 and Quiz 7 of Math 54400

## Solution of Quiz 6

Actually, I made the wrong orders…

# Linear Algebra Done Right 3rd edition

## What’s New in the Third Edition

• This edition contains 561 exercises, including 337 new exercises that were not in the previous edition. Exercises now appear at the end of each section, rather than at the end of each chapter.
• Many new examples have been added to illustrate the key ideas of linear algebra.
• Beautiful new formatting, including the use of color, creates pages with an unusually pleasant appearance in both print and electronic versions.
• Each theorem now has a descriptive name.

# Some Writings by Ziting

## 启

• Jan 3 2014

2011年至2012年，我平淡无奇的生命中发生了一点类似“天花”的小小波折，可以算是目前为止人生中最大的转折点。