Answer :
Answer: f(x) = 21 .The output is 21 when the input is 5.
Step-by-step explanation:
f(x) = 4x+1 Substitute the input, 5, for x on the right side f(x) is the equivalent of y, the output you are looking for
f(x) = 4(5) + 1
f(x) = 20 +1
f(x) = 21