function isFormula(full_formula){
   var res = true;
   var regex =  new  RegExp("[a-zA-Z_][a-zA-Z_0-9]*");
   var var_f =  new  Array();
   var_f = full_formula.split("=");
    if (!(var_f[ 0 ] ==  null  || var_f[ 1 ] ==  null )){
    var_f[ 0 ].replace(" ","");
    var_f[ 1 ].replace(" ","");
     var formula = var_f[ 0 ];
     var result = var_f[ 1 ];
     var vars =  new  Array()
     vars = formula.split( new  RegExp("[\+\/\*\-]"));
      for (var i =  0 ; i < vars.length; i++){
         if (!regex.test(vars[i]))
            res=false;
       }
     if (!regex.test(result))
    res=false;
    } else {
    res = false;
    }
     return  res;
}