Trey graphs the equations y = –x2 + 2x + 3 and y = x2 – 2x + 3 to solve the equation –x2 + 2x + 3 = x2 – 2x + 3. His graph is shown below.

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What are the solution(s) of –x2 + 2x + 3 = x2 – 2x + 3?