I don't understand why question 11 for oasis telephony is multiplying by a discount factor

It's using a formula of PV = c/r-g * 1/1+r

I thought the PV of a growing perpetuity formula was just c/r-g

This is what the textbooks say, Fundamentals of Corporate Finance by Hiller, for example. So why are we multiplying by a factor to discount? And if so, why are textbooks saying the PV of a growing perpetuity

is just PV = c/r-g?