posted by Lance on .
What are the equations of the lines through (-5,-3) and passing at distance 2sqrt5 from (5,7)
Please I really need your help. I do not know how to do this problem.
you are looking for two of the radii of the circle (x+5)^2 + (y+3)^2 = r^2
r^2 equals the square of the distance from (-5,-3) to (5,7), minus (2√5)^2
the radii are tangent to
(x-5)^2 + (y-7)^2 = 20
the points of tangency (intersections of the two circles) will give the points needed (along with (-5,-3))to write the equations of the lines