A={x丨x^2-2≥0}={x丨x≤-√2或x≥√2}
B={x丨x^2-4x+3≤0}={x丨(x-1)(x-3)≤0}={x|1≤x≤3},
A∪B={x丨x≤- 根号2或x≥1}注意到是求并集﹜