## Differential Equations and Linear Algebra (4th Edition)

We know that for a matrix $\left[\begin{array}{rrr} a & b & c \\ d &e & f \\ g &h & i \\ \end{array} \right]$ the determinant, $D=a(ei-fh)-b(di-fg)+c(dh-eg).$ Hence here $D=2(-9-5)-(-1)(9-5)+4(3-(-3))=2(-14)+1(4)+4(6)=-28+4+24=0$. thus they are coplanar, they don't span the space.