What is the equation of directrix of parabola y2 = 4bx, where b < 0 and b2 + b - 2 = 0?

The points (-a, -b), (0, 0), (a, b) and (a2, ab) are:

Given that 16p2 + 49q2 - 4r2 - 56pq = 0. Which one of the following is a point on a pair of straight lines (px + qy + r) (px + qy - r) = 0?

If 3x + y - 5 = 0 is the equation of a chord of the circle x2 + y2 - 25 = 0, then what are the coordinates of the mid-point of the chord ?