please help! describe the behavior of the equation y=−x(x+2)(x−2)(x−4)

The  leading  term  will determine  the end behavior    .....this is    -x ( x) (x) (x)  =  -x^4

The  end behavior on the  left   ( as we  move towards  negative  infinity on x)  will  be  - infinity

The end behavior on the  right  (as we move  towards positive  infinity on x)  will also be  - infinity

See the graph here to verify this  :  https://www.desmos.com/calculator/ufh2jsjxog