Question

Write an algebraic expression that illustrates the multiplicative identity

Answer 1

The multiplicative Identity says that anything times one is itself. Here's a couple  equations to show this:

15 x 1 = 15
16 x 1 = 16
132213 x 1 = 132213

Algebraic: y * 1 = y

It works for every number

Answer 2

1 * x  = x 
x * 1  =  x

are 2 examples