来自矢其的问题
【设集合A=(X|X2-3X+2=0),B=(X|x2+2(a+1)X+(a2-5)=0.若AUB=A,求实数a的取值范围】
设集合A=(X|X2-3X+2=0),B=(X|x2+2(a+1)X+(a2-5)=0.若AUB=A,求实数a的取值范围
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2020-11-08 01:58
【设集合A=(X|X2-3X+2=0),B=(X|x2+2(a+1)X+(a2-5)=0.若AUB=A,求实数a的取值范围】
设集合A=(X|X2-3X+2=0),B=(X|x2+2(a+1)X+(a2-5)=0.若AUB=A,求实数a的取值范围
A={x|x²-3x+2=0}={1,2},
B={x|x²+2(a+1)x+(a²-5)=0},
∵A∪B=A,
∴B是A的子集,又A的子集有Φ,{1},{2},{1,2}
①当B=Φ时,△=4(a+1)²-4(a²-5)