$A$ line cuts off equal intercepts on the coordinate axes. The angle made by this line with the positive direction of the $X$-axis is: (in $^{\circ}$)

The system of linear equations $ax - y + 2 = 0$ and $x + ay + 3 = 0$ has a unique solution. Then,the set of values of $a$ is . . . . . . .

If the straight line $ax + by + c = 0$ always passes through $(1, -2),$ then $a, b, c$ are

Show that two lines $a_{1}x + b_{1}y + c_{1} = 0$ and $a_{2}x + b_{2}y + c_{2} = 0$,where $b_{1}, b_{2} \neq 0$,are parallel if $\frac{a_{1}}{b_{1}} = \frac{a_{2}}{b_{2}}$.

One diagonal of a square is along the line $8x - 15y = 0$ and one of its vertices is $(1, 2)$. Then the equations of the sides of the square passing through this vertex are:

The equation of the line passing through the points $(-7, 8)$ and $(5, 2)$ is . . . . . . .