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已知M={y|y=x²-4x+3,x∈R},N={y|y=-x²+2x+8,x∈R},求M∩N 答案是{y|-1≤y≤9}
人气:233 ℃ 时间:2020-05-17 00:18:59
解答
y=x*x-4x+3=(x-2)*(x-2)-1>=-1;
y=-x*x+2x+8=-(x-1)*(x-1)+9<=9;
所以答案为-1<=y<=9.
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