You need to specify more terms in your coeffs call. The problem is that then the polynomial separates into two separate polynomials. It is not obvious to me where that originates. In any event, ‘Eq_01(1)’ appears to be the result you want.
Try this —
syms a2 a3 a4 a5 a6 a2s a3s a4s a5s a6s
IVW = 1440000*a2*a2s + 12960000*a2*a3s + 12960000*a3*a2s + 103680000*a2*a4s + 155520000*a3*a3s + 103680000*a4*a2s + 777600000*a2*a5s + 1399680000*a3*a4s + 1399680000*a4*a3s + 777600000*a5*a2s + 5598720000*a2*a6s + 11197440000*a3*a5s + 13436928000*a4*a4s + 11197440000*a5*a3s + 5598720000*a6*a2s + 83980800000*a3*a6s + 111974400000*a4*a5s + 111974400000*a5*a4s + 83980800000*a6*a3s + (6046617600000*a4*a6s)/7 + (6718464000000*a5*a5s)/7 + (6046617600000*a6*a4s)/7 + 7558272000000*a5*a6s + 7558272000000*a6*a5s + 60466176000000*a6*a6s
[Eq_01, T] =coeffs(IVW , [a2s a3s a4s])
Eq_01(1)
Eq_01(2)
.
