# Tag Info

Note that $$\left(b-\sum a[i]x[i]\right)\cdot\left(b'-\sum a'[i]x[i]\right) =bb'-b\sum a'[i]x[i]-b'\sum a[i]x[i] +\sum\sum a[i]a'[j]x[i]x[j]$$ and we can extract the coefficients $$h_0=bb'$$ h_i=-ba'...