## Calculus (3rd Edition)

The normal vector to the $yz$-plane is $\langle 1,0,0\rangle$ and using the fact that parallel planes have parallel normal vectors, we have: (a) False, since $\langle 0,0,1\rangle$ is not parallel $\langle 1,0,0\rangle$. (b) True. (c) False, since $\langle 0,a,b\rangle$ is not parallel $\langle 1,0,0\rangle$. (d) True, $x=d$ has the normal vector $\langle 1,0,0\rangle$.