Coursera Machine Learning 第一周 quiz Linear Algebra習題答案

1.

Let two matrices be

A=[4639],B=[−2−592]

What is A + B?       

 答案為B  互相加即可

[611−67]

[211211]

[2192]

[6111211]

Let  x=⎡⎣⎢⎢8251⎤⎦⎥⎥

2.What is  2∗x ?

答案C直接乘即可

[415212]

⎡⎣⎢⎢⎢⎢415212⎤⎦⎥⎥⎥⎥

⎡⎣⎢⎢164102⎤⎦⎥⎥

[164102]

3.

Let u be a 3-dimensional vector, where specifically

u=⎡⎣519⎤⎦

What is  uT ?

答案 A

[519]

[915]

⎡⎣519⎤⎦

⎡⎣915⎤⎦

4.

Let u and v be 3-dimensional vectors, where specifically

u=⎡⎣13−1⎤⎦

and

v=⎡⎣224⎤⎦

What is  uTv ?

(Hint:  uT  is a

1x3 dimensional matrix, and v can also be seen as a 3x1

matrix. The answer you want can be obtained by taking

the matrix product of  uT  and  v .) Do not add brackets to your answer.

答案4

5.Let A and B be 3x3 (square) matrices. Which of the following

must necessarily hold true? Check all that apply.

答案CD

If  C=A∗B , then C is a 6x6 matrix.

A∗B=B∗A

A+B=B+A

If A is the 3x3 identity matrix, then  A∗B=B∗A