## Destinyyyy one year ago 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)

1. Destinyyyy

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

2. james1769

6+12

3. Destinyyyy

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

4. Destinyyyy

@Nnesha

5. james1769

the same way u solved for the others

6. Destinyyyy

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

7. james1769

oh

8. Nnesha

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

9. Destinyyyy

So 3(g(x)) ?

10. Nnesha

btw A is wrong

11. Destinyyyy

How is it wrong? I followed the example.

12. Nnesha

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

13. Destinyyyy

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

14. Nnesha

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

15. Destinyyyy

Where are you getting a second x from?

16. Nnesha

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

17. Destinyyyy

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

18. Nnesha

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

19. Nnesha

where did you get that example ?

20. Destinyyyy

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

21. Nnesha

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

22. Destinyyyy

Yeah.

23. Nnesha

so (f *g)(x) means f(x) times g(x) ^^^product of two function

24. Destinyyyy

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

25. Nnesha

what do you mean by * sign is it multiplication ?

26. Destinyyyy

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

27. Destinyyyy

Yes * means multiply

28. Nnesha

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

29. Destinyyyy

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

30. Nnesha

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

31. Destinyyyy

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.

32. Nnesha

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}\]

33. Nnesha

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

34. Destinyyyy

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

35. Destinyyyy

Sorry 24..

36. Nnesha

yes 24 is correct according to that example

37. Destinyyyy

And the answer for D. is 13

38. Destinyyyy

Sorry 12.

39. Nnesha

yes right

40. Destinyyyy

Okay. Thank you.

41. Nnesha

yw