How many ordered pairs of real numbers satisfy the following system of equations?
AMC 10 A
Pick one
Solution
Answer (D): The graph of the first equation is a parabola opening downward with vertex , passing through and . The second equation is satisfied if either or . Therefore the graph of the second equation is a square with vertices , , , and together with a square with vertices , , , and . As shown below, the two graphs intersect at 5 points—, , , and 2 points on the larger square in the lower half-plane.
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