This is worth 43 points the question is in the picture

What is the missing step in this proof ?

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.

Which best explains why this triangle is or is not a right triangle ?