I'm sure the actual answer is ( B )
So 4, 9, 14, 19, ... ?
For ( B ) Why not try substitute n = 1 and look for the value of n itself?
So we substitute all inputs (n = 1, 2, 3 and 4) then the outputs should be (4,9,14,19) in order.
[tex]f(n)=5n-1\\f(1)=5-1=4\\f(2)=10-1=9\\f(3)=15-1=14\\f(4)=20-1=19[/tex]
You notice that whenever I substitute n = 1,2,3,4. I get the exact outputs that are given.
