2.( 1)∈,(2)? ,(3)∈

3.( 1){2,3,4,5}

(2){ 1,-2}

(3){0, 1,2}

4.( 1){y│y≥-4}

(2){x│x≠0}

(3){x│x≥4/5}

5.( 1)? ,? , really contained in, really contained in.

(2)∈, really contained in, really contained in, =

(3) True tolerance, true tolerance

6.A∪B={x│3≤x