-- It'll be a lot easier if you clean up the function first. You're not changing the function. You're just making it easier to read and work on without mistakes.
Notice that 3x3=9 , so the function is f(x) = 9 - 4x + 5
Combine like terms, and the function is f(x) = 14 - 4x . Much easier to work with.
-- Now, when somebody tells you to evaluate the function for some number, just take their number, write it in place of 'x',and see what you've got.
Example:
f(x) = 14 - 4x
Evaluate f(x) for x = 3.
-- Write 3 in place of 'x' in the function: f(3) = 14 - 4(3)
