Question

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

options are-

a.) -40x + 24
b.) -40x + 31
c.) -40x + 64
d.) -40x + 70

Please help? /:
and please explain to me how to solve this. I can't figure it out, it's a bit different from what was taught in the lesson, and in my notes. :(

Answer 1

I think it is D.

Answer 2

to find fog replace x with g(x) in f \(\LARGE \tt\color{midnightblue}{f(g(x))=-4[g(x)]+7}\)
then replace g(x) with 10x-6
so it becomes \(\LARGE \tt\color{midnightblue}{fog(x)=-4[10x-6]+7}\)

Answer 3

there is no i think lol
you have to find out and make sure it is^_^

Answer 4

now just FOIL 4 in (10x-6) and do the arithmetic

Answer 5

you got it!

Answer 6

Oh! so it's A!?

Answer 7

actually its B

Answer 8

Wait, no, B. it's B. I just redid it. and I got b
I missed the +7

Answer 9

Thank you!

Answer 10

yw

Answer 11

well find out, why are concerned about the options
do algebra and foil that thing and see what the result should be

Answer 12

Oh sorry! i see that you obtained the result^_^

Answer 13

I know how to Foil, but thank you, I solved my next question, based off your help, and I'm sure I got it right.

" Let f(x) = 9x - 2 and g(x) = -x + 3. Find f(g(x)). " The answer is -9x + 25

Answer 14

i thought you stuck with FOILing xD

Answer 15

Okay good to know^_^
you are welcome

Answer 16

If you want to check how I solved that -
"9[-x+3]-2
-9x+27 -2
-9x + 25

Answer 17

Correct! you got this^_^

Answer 18

Awesome! Do you mind checking my next one? it's on finding the reverse of an integer.

Answer 19

let's see

Answer 20

I have to do it first. :P

Answer 21

Sure, that's how we learn^_^

Answer 22

Let f(x) = 7x - 13. Find f-1(x).

and I got quantity of x plus 13 over 7

Answer 23

"x - 13" over "7"

Answer 24

for my f-1(x)

Answer 25

the first thing you said was correct x+13/7

Answer 26

Yes.

Answer 27

Yay^_^
you are doing great

Answer 28

Oops! I meant "x + 13" over "7" not minus

Answer 29

It's okay^_^ you got it right

Answer 30

Thank you! I feel like I really have the hang of this now.
:)

Answer 31

wait, what does f(g(2)) mean? O__O

Answer 32

Yes you are!
you are welcome,

Answer 33

it is the same thing as f(g(x))
it is just that g is evaluated at 2

Answer 34

I don't understand DX

Answer 35

well we are just substituting x with 2 in g
so it is basically the same as f(g(x)) x is for any number depending what the functions are
2 is a specific number

Answer 36

im sorry it should be 14 not 16 typo hhh

Answer 37

okay here is the thing do f(g(x)) find what it!

Answer 38

ohhh, okay, hold on. let me try and solve this one, and I'll get back to you. :)

Answer 39

okay

Answer 40

so in, the question "Let f(x) = x + 8 and g(x) = x2 - 6x - 7. Find f(g(2))." g(x) would equal -15 correct?

Answer 41

That's what I just got, so far.

Answer 42

yes correct!

Answer 43

then evalute that -15 into f

Answer 44

I shall.

Answer 45

So it's -7 !!!

Answer 46

Correct^_^

Answer 47

so f(g(2))=-7

Answer 48

Awesome!!! :3

Answer 49

the other way to do it is to find what f(g(x))
and then evaluate 2

Answer 50

f(x) = x + 8 and g(x) = x2 - 6x - 7 \(\LARGE \tt\color{midnightblue}{f(g(x))=[g(x)]+8=[x^2-6x-7]+8=\\x^2-6x+1}\)

Answer 51

if you evaluate 2 in that you get -7 too^_^

Answer 52

I like the first way. Hahaha xP

Answer 53

okay what ever is easier for you^_^

Answer 54

What about this- Let f(x) = x - 2 and g(x) = x2 - 7x - 9. Find f(g(-1)).
and f(g(-1)) is equal to -3, correct?

Answer 55

Correct!

Answer 56

You have mastery over this^_^

Answer 57

Thank you!!!

Answer 58

Welcome!