Which of the following is an even function f(x)=lxl
f(x)=x^3-1
f(x)=-3x
f(x)=3^ square root of x​

An even function is a function where positive and negative values of x give you the same result.

Where f(2) = f(-2) and f(3) = f(-3)

To formally check it, you need to evaluate f(-x) and see if you get the original function back.

Graphically, an even function is symmetrical over the y-axis.

The only graph here that does all of that is f(x) = |x|