Take a square matrix $A$ such that $$ A=BDC, $$ where $B,D,C$ are square matrices with all positive entrances; $D$ is a diagonal matrix with all entrances in the main diagonal positive.
Is it true that: if $A$ is invertible, then $B$ is invertible? Why?
$$\det(A)=\det(B)\det(D)\det(C)\ne0$$ and obviously $$\det(B)\ne0.$$