Straight Line

A straight line intersects x-axis and y-axis respectively at A(7,0) and B(0,-5).A straight line drawn perpendicular to AB meets x-axis at P and y-axis at Q.if AQ and BP intersects each other at R then show that the locus of the R is $x^2+y^2-7x+5y=0$..... I attached a image of the following instruction Then What i wanna to do?????