Question

Consider the functions f(x) = 2(x - 7) and g(x) = 2x. What is the value of (f + g)(4)?
Answer

-2

14

-6

2

Answer 1

2

Answer 2

There are two ways to tackle this problem.

The first one is to notice that
(f + g)(4) = f(4) + g(4)

So if you find f(4) and g(4), you just need to add them together.

Answer 3

The second way is to find the function (f+g)(x). Once you've found it, evaluate it for x = 4.

Answer 4

So looking at the first way, if
f(x) = 2(x - 7) and g(x) = 2x
then
f(4) = 2(4-7) = 2(-3) = -6
and
g(4) = 8

Hence f(4) + g(4) = -6 + 8 = 2.

========

Now the second way,

(f+g)(x) = 2(x-7) + 2x
= 2x - 14 + 2x
= 4x - 14

Hence
(f+g)(4) = 4(4) - 14
= 16 - 14
= 2

the same answer, which is just as well!

Answer 5

Make sense?