Y=lxl, y is a function of X.

The reason for this is the following：

The definition of a function is:

Generally speaking, there are two variables, X and Y, in a change process. If a value of X is given and a unique Y is determined based on it, Y is said to be a function of X, where X is an independent variable and Y is a dependent variable.

Y = lxl, for a given value of x, the unique y is determined accordingly,

So y is a function of x.