If the foot of the perpendicular from the origin to straight line is at the point ( 3, - 4). Then the equation of the line is

Let O(0,0) be the origin and P(3, -4) be the given point.      Slope of OP=−43     Slope of the required line =34Clearly, required line passes through P( 3, - 4) and is perpendicular to OP. So, its equation is   y+4=34(x−3) or, 3x−4y−25=0The equation of a line passing through two points (x1, y1) and (x2, Y2), is            y−y1=y2−y1x2−x1x−x1