OG详解-OG2 数学2 Q11

Choice B is correct. Since the point (x, y) is an intersection point of the graphs of the given equations in the xy-plane, the pair  (x, y) should satisfy both equations,  and thus is a solution of the given system. According to the first equation,  y = 76.  Substituting 76  in place of y  in the second equation yields  x² -5 = 76. Adding 5  to both sides of this equation yields  x² = 81. Taking the square root of both sides of this equation yields two solutions: x = 9 and x =-9. Of these two solutions, only -9  is given as a choice.
Choice A is incorrect and may result from conceptual or calculation errors.  Choice C is incorrect and may result from conceptual or calculation errors.  Choice D is incorrect. This is the value of coordinate y , rather than x , of the intersection point (x, y).