Can you please help with eigenvalues of matrix?

Question

From below choices, select all correct approaches for finding the eigenvalues of matrix

A.) First form a new matrix ,  compute its determinant and then find the roots of the polynomial equation: The roots are the eigenvalues.

B.) Use the elementary row or column operations to create two zeros in one row or one column in 

 first, let's call the new matrix Compute  and then solve   . The roots are the eigenvalues of .

C.) Form a new matrix , then use the elementary row or column operations to create two zeros in one row or one column of this new matrix. Compute  and then solve The roots are the eigenvalues of .

D.) The eigenvalues of a square matrix are its diagonal entries so the 3 eigenvalues of  are: 

Answer 1

The correct answer is A). If you spend 10 minutes reading your textbook instead of asking for help, you would know the answer.