matlab syms 运行出错

matlab syms 运行出错>> syms x a b c f=sym('a*x^2+b*x+c')findsym(f,4)y(1)=limit(f,x,1)y(2)=limit(f,1)y(3)=limit(f,a,2)y(4)=limit(f,b,1)yAttempt to execute SCRIPT syms as a function.Error in ==> jixian at 1syms x a b c 请问是为什么呢?