var query = new esri.tasks.Query();
query.returnGeometry = true;
query.objectIds = [0,];
var queryTask0 = new esri.tasks.QueryTask("http://myserver:6080/arcgis/rest/services/BackLayers/MapServer/8");
queryTask0.execute(query, function (featureset) {
var geometrytype = feature eset.geometryType;
});