Question y-76-y

2.3 Systems Involving Nonlinear Equations - Line + parabola intersections
0:00

y = 76
y = x 2 - 5

The graphs of the given equations in the xy-plane intersect at the point (x,y). What is a possible value of x ?

A.

- 76 5

B.

-9

C.

5

D.

76

y = 76 y = x 2 - 5 The graphs of the given equations in

Medium-difficulty · SAT Math · Systems Involving Nonlinear Equations — Line + parabola intersections. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

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 x 2 - 5 = 76 . Adding 5 to both sides of this equation yields x 2 = 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.