Hi

The following question, can someone tell me if this is the right method of doing it.

If, $\displaystyle X =\begin {bmatrix}x \\ y \\ z \\\end {bmatrix}$ and $\displaystyle D = \begin {bmatrix} 0\\ 0\\ c\\ \end{bmatrix}$, find conditions on a, b and c so the system of equations represented by CX = D has an infinite number of solutions.

previous question asked to find det C = $\displaystyle \begin{bmatrix}1 & 5 & 1 \\ 1 & 6 & -1 \\ 2 & a & b \\ \end{bmatrix}$

det C = b +2a-22

i made b=0 to find a which equals 11 therefore det C =0 and c=0 when i made the equation $\displaystyle X=C^{-1}D$

P.S