MATLAB 运行sym指令出错，win764位版本2009a，怎么结局？

>> syms a??? Undefined function or method 'symenginelocation' for input arguments of type 'char'.Error in ==> mupadengine.mupadengine>mupadengine.mupadengine at 72                    symenginelocation(path);Error in ==> D:\Yingwenruanjian\Matlab\MATLAB\toolbox\symbolic\symengine.p>symengine at 24Error in ==> sym.sym at 69eng = symengine;Error in ==> syms at 77      assignin('caller',x,sym(x));什么意思，求指导