Animating Using Action Script

i have been using action script to make a simple sprite move from one edge of the stage to the other and decreasing in size at the same time and using easing, here is the script that i have made.

import mx.transitions.Tween;
import mx.transitions.easing.*;
var myTween = new Tween(introanthead_mc, "_width", Strong.easeInOut, 1000, 100, 33, false);
var myTween = new Tween(introanthead_mc, "_height", Strong.easeInOut, 1000, 100, 33, false);
var myTween = new Tween(introanthead_mc, "_x", Strong.easeInOut, 13.7, 649, 33, false);
var myTween = new Tween(introanthead_mc, "_y", Strong.easeInOut, 587.7, 292, 33, false);

but the shape of the sprite does not stay the same size can you help??
p.s.
(and we don't want to use the time line)

100, 10, 33, false);