Thank you for your answer, but I already read this site (my citation is from this website) and didn't found the right code.
Maybe I should give you my code to underline my problem:
<!-- <script type="text/javascript" src="//www.geogebratube.org/scripts/deployggb.js"></script>
<script type="text/javascript">
applet1 = new GGBApplet({material_id: "xxxxxxx"}, true);
applet2 = new GGBApplet({material_id: "xxxxxxx"}, true);
window.onload = function()
{applet1.inject('applet_container1', 'preferHTML5');
applet2.inject('applet_container2', 'preferHTML5'); }</script>
<div style="width:843px;height:607px;display:block" id="applet_container1"></div>
<div style="width:843px;height:607px;display:block" id="applet_container2"></div>
<input onclick="document.ggbApplet.setVisible('a',true)" value="Zeige Lösung" type="button"> -->
But the input always changes applet2.