Is there a way to ask Maple to write an expression in terms of other expressions? Eg.

f[1] := v[1]+v[2];
 f[2] := v[1]*a[1]+v[2]*a[2];
 f[3] := v[1]*a[3]*a[4]+v[2]*a[5]*a[6];
 f[4] := v[1]*a[1]*a[4]+v[2]*a[2]*a[6];
 f[5] := v[1]*a[3]*a[7]*a[8]+v[2]*a[5]*a[9]*a[10];
 f[6] := v[1]*a[3]*a[4]*a[8]+v[2]*a[5]*a[6]*a[10];
 f[7] := v[1]*a[1]*a[7]*a[8]+v[2]*a[2]*a[9]*a[10];
 f[8] := v[1]*a[1]*a[4]*a[8]+v[2]*a[2]*a[6]*a[10];