5. which statement is not true?
if x = 1, then x2 = 1.
if x2 = 1, then x = 1.
if x= -1, then x2 = 1.
x2 = 1 if and only if x = 1 or x = -1.

is NOT true.

Step-by-step explanation:

1.

......True

( 1 )² = 1

2.

If ........ NOT True

∴ x =± 1     .........this is correct

3.

......True

( -1 )² = 1

4.

x2 = 1 if and only if x = 1 or x = -1. .........True

( 1 )²  = 1

( -1 )² = 1

answer: (1,3) and (-2,0) i think.