Question

HELP! Medal and fan to the best help:)
Let f(x) = 9x - 2 and g(x) = -x + 3. Find f(g(x)).

-9x - 2

-9x + 5

-9x + 25

-9x + 27

Answer 1

just substitute the x on function f(x) for (-x+3)

Answer 2

Alright what do I do next?

Answer 3

well you have
f(x) = 9x -2
9(-x+3) -2
= -9x + 27 -2
= -9x + 25

Answer 4

That makes so much sense!! Think that you can help me with another few?

Answer 5

sure

Answer 6

Let f(x) = -4x + 7 and g(x) = 10x - 6, find f(g(x)).

-40x + 24

-40x + 31

-40x + 64

-40x + 70

Answer 7

same process as previews problem
substitute the x from f(x) with (10x-6)

Answer 8

-40x + 64?

Answer 9

how did you get to +64 ??

Answer 10

you have
f(x) = -4x + 7
= -4(10x -6)+7
= -40x +24 + 7
= -40x + 31

Answer 11

Why would we not use that equation (-4x + 7) on the other side (g(x) = 10x - 6)?

Answer 12

the question is f(g{x}), that means you are inserting g(x) inside the function f(x)

Answer 13

if the question had been g(f{x}), then you insert f(x) inside g(x)

Answer 14

Oh okay, this is all making sense now, its all about reading the question properly!
Let f(x) = 12/4x + 2 Find f(-1).

-6

-2

2

6

How would I go about solving this?

Answer 15

@ivettef365 ?

Answer 16

on his one just substitute the x from f(x) for -1

Answer 17

so you have

12
---------
4x + 2

Answer 18

solve as follows:

12
---------------
4(-1) + 2

Answer 19

6?

Answer 20

Since you've been helping me, this is all making so much sense now

Answer 21

Let f(x) = x + 8 and g(x) = x2 - 6x - 7. Find f(g(2)).

-7

-3

10

33
@ivettef365 ??

Answer 22

When there is the "2" In f(g(2)) what does that mean and how would I go about solving that?

Answer 23

on the previews quetions you have 12 /-2 = -6
remember when dividing a positive with negative answer is negative

Answer 24

I'm glad I can help

Answer 25

on this problem,
f(x) = x + 8 and g(x) = x2 - 6x - 7. Find f(g(2)) first step substitute the x for 2 on g(x)

g(x) = x^2 - 6x -7
2^2 - 6(2) -7
4 -12-7
4 -19 = -15

Answer 26

now you can substitute the x from f(x) for -15, try it to see if you get to answer

Answer 27

-7 right?

Answer 28

@ivettef365

Answer 29

correct

Answer 30

Let f(x) = x - 2 and g(x) = x2 - 7x - 9. Find f(g(-1)).

-21

-3

3

21

Answer 31

now you try doing it and I let you know if is correct.

first step substitute the x from g(x) for -1

Answer 32

I keep running into this problem, (-1)2 - 7(-1) - 9
-2 + 7 - 9 = 4


4 - 2 = 2 and that is none of the possible answers

Answer 33

0?

Answer 34

sorry, my mistake now so (-1)^2 = 1
so you have 1 +7-9 = ??

Answer 35

-1!

Answer 36

correct, now substitute the -1 for the x on f(x)

Answer 37

-3!

Answer 38

correct, good job

Answer 39

Let f(x) = 2x + 2. Solve f^-1(x) when x = 4.

1

3

4

10

This one is confusing me because of the "f^1" how would I go about doing this and equations like this?

Answer 40

@ivettef365

Answer 41

that is the inverse function

Answer 42

sorry, erased it by mistake, here it is again, to find the inverse function
f(x) = 2x + 2 you need to write the function as follows:

x = 2y + 2
x-2 = 2y

x - 2
------- now substitute the x for the 4
2

Answer 43

1:)

Answer 44

Let f(x) = 2x - 6 Solve f-1(x) when x = 2.

-5

4

-2

7
Can you show me how I would re-write the inverse function to solve this one?

Answer 45

I was a little unclear about how to re-write it @ivettef365

Answer 46

sorry, I went a little bit fast, because I am at work, and boss was calling me
but let me explain, the inverse of a function is just to isolate the x, so in order to do that you get the function f(x) = 2x + 2 and re-write it as

x = 2y + 2 ( I substitute the x for y, that way I isolate the y that is on my x value place)

x - 2 = 2y (I transfer the 2 to the other side, to transfer you have to change the sign)

x - 2
----- = y (now I divided by 2 on both sides, and the y stays by itself because
2 2y/2 = y) and there you have the inverse

Answer 47

now try to do the inverse on this problem you have f(x) = 2x - 6

you write it as x = 2y - 6 (isolate the y)

Answer 48

x-6/2 = y?

Answer 49

remember when you switch a number to the other side need to change the sign

Answer 50

x+6/2 = y then right?

Answer 51

good job, now just substitute the x for 2 that is the easy part

Answer 52

4!:) Thank you so much for all of your help in teaching me these topics!

Answer 53

your welcome :)