Question

If f(x) = 4x - 7 and g(x) = 3x + 9 find (f+g) (5)

Answer 1

Answer: (f+g)(5)=37

Step-by-step explanation:

(f+g) (5) is the same as saying f(5)+g(5). Since we are given f(x) and g(x), we can use them to solve. There are two ways to solve. One is to find f(5) and g(5), and then add them together. Another way is to do (f+g)(x), then plug in x=5. I will show both methods.

Method 1

f(5)=4(5)-7                       [multiply]

f(5)=20-7                         [subtract]

f(5)=13

g(5)=3(5)+9                     [multiply]

g(5)=15+9                        [add]

g(5)=24

(f+g)(5)=13+24                [add f(5) and g(5)]

(f+g)(5)=37

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Method 2

(f+g)(x)=4x-7+3x+9         [combine like terms]

(f+g)(x)=7x+2

(f+g)(5)=7(5)+2                [plug in x=5]

(f+g)(5)=35+2                  [add]

(f+g)(5)=37

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Now, we know that (f+g)(5)=37. We confirmed this with both methods.