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Let u = {1,2,3,4}, a = {x vertical line X & # 178; - 5x + M = 0} If a is contained in U, find the range of M The answer is m = 4 or M = 6 or m greater than 25 out of 4
x²-5x+m=0
A is contained in U
(1) A is an empty set, that is, the equation has no solution
∴ △=25-4m25/4
(2) If a is not an empty set, then the roots of the equation can only be numbers in 1,2,3,4
∵ the sum of two is equal to 5 (Veda's theorem)
Two are 1,4 or 2,3
1 * 4 = m or 2 * 3 = m (Veda's theorem)
‖ M = 4 or M = 6
In conclusion, M = 4 or M = 6 or M > 25 / 4
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