universal data

Chapter 101 The book friend group is here! !

建了个书友群，群号是：7-0-6-8-0-0-5-8-9
There will be a problem when joining a group, and the problem is below.

Well... everyone, please listen to the question!It's time to test whether you are a top student!
………………

Here is a system of homogeneous linear equations
X1+X2+2X3-X4=0
2X1+X2+X3-X4=0
2X1+2X2+X3+2X4=0
The rank of the coefficient matrix of this equation system is the answer to the group! !

Welcome everyone to join the top academic exchange group! !Warm welcome! !

(End of this chapter)