First lets work out the length of the top side which joins the points (-1,7) and (-5,5):-
this = sqrt ( (7-5)^2 + (-1 - (-5)^2 )
= sqrt (4 + 16)
= sqrt 20
Now find length of the longer side which is distance between the points (-1,7) and (4, -3)
this is sqrt ( (-1 - 4)^2 + (7 - -3)^2)
= sqrt 125
Area of the rectangle = sqrt 20 * sqrt 125
= sqrt 2500
= 50 units^2 Answer