We are asked to find the inverse of the following matrix, provided the inverse exists: $$ \left[\begin{array}{rrr} 1 & a & b+c\\ 1 & b & a+c\\ 1 & c & a+b \end{array}\right] $$

I cannot seem to arrive at any definitive solution. What I do know is that we augment the matrix with the identity matrix and perform elementary row operations such as addition, subtraction and multiplication.


Hint: $a_{i3} = (a+b+c)a_{i1}-a_{i2}$.

  • $\begingroup$ Any more hints is appreciated $\endgroup$ – user4640007 Apr 11 '15 at 6:16
  • $\begingroup$ @user4640007: Columns are not linearly independent, hence $\det=0$, inverse does not exist. $\endgroup$ – g.kov Apr 11 '15 at 6:37
  • $\begingroup$ Thanks for your response. An answer with more clarification for others is appreciated. $\endgroup$ – user4640007 Apr 11 '15 at 6:39

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