The system of linear equations x + y + z = 2 , 2x + 3y + 2z = 5 , 2x + 3y + (a^{2} – 1)z = a + 1

- (1) is inconsistent when a = 4
- (2) has infinitely many solutions for a = 4
- (3) has a unique solution for | a| = √3
- (4) is inconsistent when |a| = √3