put a vector in the form f(x)+g(x)u

Hello,

I have symbolic variables x1,x2,x3,x4,x5,x6,x7,x8 and u.

I have a vector [3*x1^2+2*sqrt(x3)+x1*x2*u;x5*x_8^2+u*sqrt(x5)*x2^2+5*x1] I want to have a way to put these kind of vectors automatically in the form f(x1,x2,...,x8)+g(x1,x2,...,x8)*u.

How can I do this with matlab? (after this small example I want to apply the method to very big vectors of symbolic variables)