If the points $A(x, -1), B(2, 1)$ and $C(4, 5)$ are collinear, then $x=?$

If $\mathrm{\theta }$ is the angle between $AB$ and $CD$ with $A(0, 0), B(2, 3), C(2, -2)$ and $D(3, 5)$, then $\tan \mathrm{\theta }$ = ?

If $A(3, x), B(2, 7), C(-1, 4)$ and $D(0, 6)$ are the points such that $AB\parallel CD$ then $x=?$

If $A(-2, 6), B(4, x), C(3, -3)$ and $D(5, -9)$ are the points such that $AB$ is perpendicular to $CD$, then $x=?$

The vertices of a parallelogram $ABCD$ are $A(0, 2), B(-2, -1), C(4, 0)$ and $(2, 3)$ and is the angle between the diagonals $AC$ and $BD$. Then, $\tan \theta =?$