If the solution of equation x2-5x + 6 = 0 and equation x2-x-2 = 0 is m, then the number of elements in M is () A. 1B. 2C. 3D. 4

∵ the solution of equation x2-5x + 6 = 0 is X1 = 2, X2 = 3 ∪ the set of solution of equation x2-5x + 6 = 0 is {2, 3}. Similarly, the set of solution of equation x2-x-2 = 0 is {- 1, 2}. Therefore, the set M = {2, 3} ∪ {- 1, 2} = {- 1, 2, 3} has three elements in total

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