Evaluate $(1996)^2 - (1995)(1997)$.

1996^2 - (1995)(1997)

1996^2  - (1996 - 1)(1996 + 1)

1996^2  - [ 1996^2  - 1]  =

1

Note that, in general...

a^2 - (a - 1) (a + 1)  =

a^2 - [a^2 - 1]  =  

1

Good thinking Chris