Question 1208181
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If you have nothing to do, you may place "x" instead of the question mark,
equate the determinant of the matrix to zero and solve for x.



Or, alternatively, you may require the sum of elements of the matrix to be equal to zero. 
Then you obtain another equation to determine the value of x.


Again, if you have nothing to do, you may entertain yourself doing it.



Third possible entertainment is to equate the trace of the matrix to zero (the sum of the diagonal elements)
and find x from this equation.



Fourth possibility is to place any number instead of x, for example,


        73,  -289,  {{{sqrt(3)}}},  e,  {{{pi}}},   {{{e^pi}}}  or   {{{pi^e}}},


since nothing in the problem prohibits you to do it.



Thus, if you really have nothing to do and struggle of it, you may have several ways to entertain yourself.



The only thing which I do not understand, is THIS: do you really think that at this forum I will entertain you ?



If you think so, you make very crude mistake: this forum is not for puzzles.


At this forum the tutors perform another job: we work to teach real students to real Math.


To come here for puzzles is the same as to come to a grocery store for hardware.



If you are seeking help for puzzles and want others entertain you and generally make 
your job substituting yourself, find another web-site/forum in the Internet.



If you stop posting your puzzles to this forum, we, the tutors, will be infinitely happy.



Have a super-nice day.