设A={x|x2-3x+2=0}B={x-ax+2=0}若A∪B=A求a
问题描述:
设A={x|x2-3x+2=0}B={x-ax+2=0}若A∪B=A求a
答
x²-3x+2=0
(x-1)(x-2)=0
x=1或x=2
A={1,2}
B={x²-ax+2=0}
A∪B=A,则B可以为空集Φ,{1},{2},{1,2}
B为空集,方程判别式