Let A be a $3\times4$ matrix of rank $2$ for some real numbers $a$ and $b$. What is the value of $b$?
where, $$A = \begin{pmatrix} 1 & 1 & 2 & 2 \\ 1 & 1 & 1 & 3 \\ a & b & b & 1 \\ \end{pmatrix}$$
How to approach this?
I tried finding the row reduced echelon form. But I could not proceed further, any hint will be appreciated. Thanks in advance