echo PHP within PHP?

I am not good with PHP but I am learning…. quick question. Why can’t I echo PHP within a PHP tag?

Here is what I am trying to do… but it’s not working:

<?php
function my_super_admin_widget() {
global $blog_id;
if( $blog_id == '42' ) {
echo '<?php if (function_exists('easing_slider')){ easing_slider(); }; ?>'; }
}
?>

Thanks for your help!