(21)(22)(From Unit 1, Lesson 6.)Here is a recursive definition for a sequence f:f(0)=15,f(n)=f(n−1)−4 for n≥1. The definition for the nth term is f(n)=15−4⋅n for n≥0.a. Explain how you know that these definitions represent the same sequence (23)b. Select a definition to calculate f(25), and explain why you chose it.(From Unit 1, Lesson 8.)21. Enter the part of the recursive equation that describes the starting term.Type a response