M={x,x^2-3x+2=0}
={x,(x-1)(x-2)=0}
={1,2}
N={x,x^2-ax+(a-1)=0}
={x,(x-1)[x-(a-1)]=0}
={1,a-1};
若N不是M的真子集,则
a-1不等于1,即a不等于2,写成集合的形式为
{a,a不等于2}