remove child

hello!

i have chalange with remove child

i wrote this code

in button_2  the code removed olny the child from empty but not from empty1

what's wrong in the code??

this["empty"].addChild(new lib["picword14"]());
this["empty1"].addChild(new lib["picword14"]());

this.button_2.addEventListener("click", fl_ClickToGoToAndPlayFromFrame_2.bind(this));

function fl_ClickToGoToAndPlayFromFrame_2()
{
this["empty"].removeChildAt(); 
this["empty1"].removeChildAt();
}

this.button_3.addEventListener("click", fl_ClickToGoToAndPlayFromFrame_3.bind(this));

function fl_ClickToGoToAndPlayFromFrame_3()
{
this["empty"].addChild(new lib["picword14"]());
this["empty1"].addChild(new lib["picword14"]());
}