Thread Subject: Solve Array of symbolic functions

if A1 is an array of symbolic funtions:
A1=
              -a1+a2-a3+a4
 -1/27*a1+1/9*a2-1/3*a3+a4
  1/27*a1+1/9*a2+1/3*a3+a4
               a1+a2+a3+a4

Why can't I use solve like:

[a1, a2, a3, a4] = solve('A1(1)=1', 'A1(2)=0', 'A1(3)
=0', 'A1(4)=0', a1, a2, a3, a4);

But must I manually insert all the values of A1 like this?:

[a1, a2, a3, a4] = solve('-a1+a2-a3+a4=1', '-1/27*a1+1/9*a2-
1/3*a3+a4=0', '1/27*a1+1/9*a2+1/3*a3+a4=0', 'a1+a2+a3+a4=0',
 a1, a2, a3, a4)[a1, a2, a3, a4] = solve('-a1+a2-
a3+a4=1', '-1/27*a1+1/9*a2-
1/3*a3+a4=0', '1/27*a1+1/9*a2+1/3*a3+a4=0', 'a1+a2+a3+a4=0',
 a1, a2, a3, a4)