If the lines y + px = 1 and y - qx = 2 are perpendicular, then which one of the following is correct?

If A, B and C are in AP, then the straight line Ax + 2By + C = 0 will always pass through a fixed point. The fixed point is

If the image of the point (-4, 2) by a line mirror is (4, -2), then what is the equation of the line mirror?

$\rm tan^{-1}x+cot^{-1}x=\frac{\pi}{2}$ holds, when