MATLAB计算中的小问题,那位大神帮帮忙!

[stormbird]

我输入
>> syms l xov ei t v x g0 ya faiza yb faizb;
>> fa1=int(ei*t*v^2*l^6/(g0*l^3+ya*l^3-3*x^2*ya*l+2*ya*l^3+faiza*x*l^3-2*faiza*x^2*l+faiza*x^3*l+3*x*l^2-2*yb*x^3-faizb*x^2*l^2*faizb*x^3*l)^1,x,l-xov,l);fa1=simple(fa1)
时可得结果......
单输入
>> syms l xov ei t v x g0 ya faiza yb faizb;
>> fa1=int(ei*t*v^2*l^6/(g0*l^3+ya*l^3-3*x^2*ya*l+2*ya*l^3+faiza*x*l^3-2*faiza*x^2*l+faiza*x^3*l+3*x*l^2-2*yb*x^3-faizb*x^2*l^2*faizb*x^3*l)^2,x,l-xov,l);fa1=simple(fa1)
Warning: Explicit integral could not be found.
时得
> In C:\MATLAB6p5\toolbox\symbolic\@sym\int.m at line 58

fa1 =

int(ei*t*v^2*l^6/(g0*l^3+3*ya*l^3-3*x^2*ya*l+faiza*x*l^3-2*faiza*x^2*l+faiza*x^3*l+3*x*l^2-2*yb*x^3-faizb^2*x^5*l^3)^2,x = l-xov .. l)
两个输入只是分母中的幂次由1改为2就不行了,谁帮帮我啊!感激不尽!在这里先谢过了!