Question 6: You list an expansion matrix and linear equations.

x+y= 1

x+2y=0

-x+y+z=-2

X=2，y=- 1，z= 1。

The answer is β=2α 1-α2+α3.

Question 8: Error

The correct one should be | 2a | = 2 n | a |

Question 9: Error

The column vector of should be linearly independent.

Question 10: Error

If a and b are irreversible matrices, they are invalid.

Question 1 1: Error

You can give a counterexample.

Question 12: Correct.