Question

For f(x)=3x and g(x)=x+6, find the following functions. A. (f*g)(x) B. (g*f)(x) C. (f*g)(2) D. (g*f)(2)

Answer 1

For A. I got 3x+18
For B. I got 3x+6
I'm stuck on C.

Answer 2

6+12

Answer 3

I assume that's the answer for C.. I want to know how to solve it.

Answer 4

@Nnesha

Answer 5

the same way u solved for the others

Answer 6

If I solve it the same way I did the other two I get stuck at 3(g(2))

Answer 7

oh

Answer 8

substitute x for g(2) into f(x) function

Answer 9

So 3(g(x)) ?

Answer 10

btw A is wrong

Answer 11

How is it wrong? I followed the example.

Answer 12

when we multiply same bases we should `ADD` their exponents
so 3x times x =?

Answer 13

This is my first time doing this type of problem so I dont really know what im doing.

Answer 14

x is same as x to the one power
apply the rule when we multiply same bases we should `add` exponents \[\huge\rm x^m \times x^n=x^{m+n}\]

Answer 15

Where are you getting a second x from?

Answer 16

we should multiply g(x) by f(x)

Answer 17

My example told me to do this-
(f*g)(x)= f(g(x))= 3(g(x))= 3(x+6)= 3x+18

It doesn't have x^2

Answer 18

well (f*g)(x) means f(x) times g(x)

Answer 19

where did you get that example ?

Answer 20

My examples says (f*g)(x) means f(g(x)). My online class on Pearson. Its a system example.

Answer 21

f(g(x)) composition means (f o g)(x) where you should substitute x for g(x) into f(x) function

Answer 22

Yeah.

Answer 23

so (f *g)(x) means f(x) times g(x)


^^^product of two function

Answer 24

I entered my answer for the assignment and it says its correct.

Answer 25

what do you mean by `*` sign is it multiplication ?

Answer 26

My examples for C does this-

f(x)=3x g(x)=x+7
(f*g)(5), find the value of (f*g)(x) when x=5.
(f*g)(x)= 3x+21
(f*g)(5)= 3(5)+21
36

Answer 27

Yes * means multiply

Answer 28

looks at this
http://home.windstream.net/okrebs/page42.html
(f*g)(x) means f(x) times g(x)

Answer 29

For that example above its not clear where the 21 comes from.

Answer 30

x+6 or x+7 ?
g(x)^^

Answer 31

x+7 is the example from the system. x+6 is the problem im working on. And the link you posted- I worked on that 2 problems ago.

Answer 32

well in that example
the replaced x from with x+7 in f(x) function \[\large\rm f(x)=3\color{Red}{x} ~~~g(x) ~~~\large\rm f(x+7)=3(\color{ReD}{x+7})\]=\color{Red}{x+7}\]

Answer 33

so when you distribute parentheses by 3 you will get 3x +21
3 times 7 = 21

Answer 34

Okay. I thought it was that but wasn't sure. So the answer for C is 33.

Answer 35

Sorry 24..

Answer 36

yes 24 is correct according to that example

Answer 37

And the answer for D. is 13

Answer 38

Sorry 12.

Answer 39

yes right

Answer 40

Okay. Thank you.

Answer 41

yw