for f(x) =5 - 2x find f(a+3)

Question

for f(x) =5 - 2x find f(a+3)

Answer 1

f(a+3) = -2a - 1

Substitute (a+3) into f(x) to obtain  f(a+3) = 5 - 2(a+3)

Then distribute the 2 to obtain f(a+3) = 5 - 2a - 6

Then subtract 6 from 5 and voila!  f(a+3) = -2a - 1