用列举法表示下列集合A={x丨x^2=9} B={x∈N丨1≤x≤2} C={x丨x^2-3x+2=0}
问题描述：
用列举法表示下列集合A={x丨x^2=9} B={x∈N丨1≤x≤2} C={x丨x^2-3x+2=0}
答
A={x丨x^2=9}={3,-3}
B={x∈N丨1≤x≤2} ={1,2}
C={x丨x^2-3x+2=0}={1,2}