Answer:
1. Proved down
2. proved down
3. f(10) = -20 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5
Step-by-step explanation:
Let us explain how to solve the question
∵ f(0) = -20, f(n) = f(n - 1) - 5 for n > 1
→ That means we have an arithmetic sequence with constant
difference -5 and first term -20
1. → f(1) means we need to find the second term, which equal the
term - 5
∵ f(1) means n = 1
∴ f(1) = f(1 - 1) - 5
∴ f(1) = f(0) - 5
∵ f(0) = -20
∴ f(1) = -20 - 5 → Proved
2. → f(3) means we need to find the third term, which equal the
second term - 5
∵ f(3) means n = 3
∴ f(3) = f(3 - 1) - 5
∴ f(3) = f(2) - 5
→ f(2) = f(1) - 5
∵ f(1) = -20 - 5
∴ f(2) = [-20 - 5] - 5 = -20 - 5 - 5
∴ f(3) = [-20 - 5 - 5] - 5
∴ f(3) = -20 - 5 - 5 - 5 → Proved
3. → From 1 and 2 we notice that the number of -5 is equal to n,
at n = 1 there is one (-5), when n= 3 there are three (-5)
∵ n = 10
∴ There are ten (-5)
∴ f(10) = -20 - 5(10)
∴ f(10) = -20 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 - 5 → Proved
