When using the inspection method, which number would you add to (and subtract from) the constant term of the numerator in this expression so the polynomial in the numerator will have(x+4) as a factor?

Asales representative from a local radio station is trying to convince the owner of a small fitness club to advertise on her station. the representative says that if the owner begins advertising on the station today, the club's total number of members will grow exponentially each month. she uses the given expression to model the number of club members, in hundreds, after advertising for t months.