Question

F(n+1)=f(n)-5. If f(1)=100, what is f(6)

Answer 1

75

Explanation:

Given:

f(1) = 100

f(n+1) = f(n) - 5

Solve for:

f(6)

Solution:

f(1) = 100

f(2) = f(1) - 5 = 100 - 5 = 100 - 1 x 5 = f(1) - 1 x 5

f(3) = f(2) - 5 = 100 - 5 - 5 = 100 - 2 x 5 = f(1) - 2 x 5

...

f(n) = f(n - 1) - 5 = 100 - (n-1) x 5 = f(1) - (n-1) x 5

=> f(6) = f(1) - (6-1) x 5 = 100 - 5 x 5 = 100 - 25 = 75

Hope this helps!