hi again Recall a relation ~ is an equivalence relation if: a. x ~x i .e. x is related to x b. x~y implies y~x c. x~y nad y~z implies x~z NOw if you look at 1, the condition (a) fails since x is not equal to -x. For 2, again (a) fails since xis not equal to 3x. You can check yourself that for 3, 4 and 5 all three conditions hold. have fun with math.