functions and relations

User Generated

Nylffn1997

Mathematics

Question Description

1)  What is f(-2) for f(x) =  ?

2) What is f(-4) for f(x) =   ?

3) Find (f – g)(x) if f(x) = 2x – 3 and g(x) = 4x + 8.

4) Find (f + g)(x) if f(x) =   and g(x) = -x - 3.

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Explanation & Answer

You are missing information in some cases. 

1) You need to know the function f(x) and replace x by -2

Ex: f(x)=x+2  then f(-2) = -2+2=0 

2) You need to know the function f(x) and replace x by -4

Ex: f(x)=x+2 then f(-4)= -4+2 = -2

3) You have all the information:

(f-g)(x) = f(x) - g(x) = 2x-3 - (4x+8) 

                              = 2x -3 - 4x - 8   changing the signs inside the parenthesis

                               = (2x - 4x) + (-3 - 8)  Regrouping       

                               = -2x + (-11 )          because     -a-b = - (a+b)

                               = -2x - 11                because +*- = - 

4) You have g(x) but you need to have also f(x)

(f+g)(x) = f(x) + g(x) = f(x) + (-x-3) = f(x) - x - 3

VyrnanC (262)
Carnegie Mellon University

Anonymous
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