x²-1≥0(x+1)(x+1)≥0x≥1或x≤-1备注：大于号取两边，小于号取中间
x^2-1>=0x^2>=1x<=-1或x>=1
x^2-1≥0x^2≥1当x＜0时x-1x≥0时x≥1
x^2-1>=0x^2>=1-1>=x或x>=1
