Đáp án: Dài quá 31 thôi nha/
Giải thích các bước giải:
1) 2,1,-1,-2 2)x < 3 3) 4, -4 4) 3,4,5,-3,-4,-5 5)3,2,1,-1,-2,-3 6)x < 5 7)5,4,3,2,1,-1,-2,-3,-4,-5
8) x< 9 9) 9,8,7,6,5,4,3,2,1,-1,-2,-3,-4,-5,-6 10) x < 6 11) x< 2
12) x ≤ 1 13) x=1 14) mờ 15) mờ 16 mờ
17) x < 5 18) x ≤ 17 19) x <-3 20)x < 15