Question

More with functions: QUICK QUESTION

Which of the equations do I do first? G or F?
For example:

If f(x)=x+4, g(x)=5x-1 what is f + g of -3?
I know how to do the equation but I don't know which one I should substitute -3 for x

Answer 1

\[(f+g)(-3)=f(-3)+g(-3)\]

Answer 2

so f first right?

Answer 3

is it always going to be f first?

Answer 4

because one of the equations I tried said what is g of f of -1
and I had to do F first

Answer 5

guys please help :(

Answer 6

hmm, is an addition, the order in whiich the sum will be conducted won't matter

Answer 7

It really doesn't matter which one you do first for this particular problem.

Answer 8

2+ 3 = 5
3 + 2 = 5

x + 3x = 4x
3x + x = 4x

Answer 9

okay if its addition it doesn't matter what if its multiplication?

Answer 10

on multiplication, it won't matter, if you end up doing f(x) * g(x)
same, the order doesn't matter in multiplication

Answer 11

but I tried one that said f of g of 2 im guessing it was multiplication and i did it both ways and I got two different answers

Answer 12

hehe, w00t, same 2 functions?

Answer 13

\(f(g(2))\)?

Answer 14

You first calculate g(2), and then you plug that value in for x in f(x).

Answer 15

hmm yeah like that austin

Answer 16

ohhh, that's not multiplication then

Answer 17

yeah thats what I did but how did you know you do g first?

Answer 18

oohhhh is it because its in parantheses?

Answer 19

because is g(2) is the DOMAIN of f(x), so you evaluate g(2) first, so you can pass it to f(x)

Answer 20

what do you mean domain?

Answer 21

You have \(f(x)\) and \(g(x)\)
If you have \(f(g(x))\), that means that you would plug in \(g(x)\) for all instances of x in \(f(x)\).
BUT because in your problem, it is \(g(2)\), that means that you have to plug in 2 for all instances of x in \(g(x)\). Then you plug that value into \(f(x)\).

Answer 22

I get that plug in part and how to get the answer I just don't know which one to do first wether its f first or g first

Answer 23

\(\bf f(x) = x^4 + x^3 + x^2...\\
g(x) = whatever\\
f(g(x)) = (whatever)^4 + (whatever)^3 + (whatever)^2 ...\)

Answer 24

Find \(f(g(3))\)

\(f(x)=2x+3\)
\(g(x)=5x-2\)

\(g(3)=5(3)-2=13\)
\(f(g(3))=2(13)+3=29\)

Answer 25

Ii understand how to do that guys its just I don't know which to plug in FIRST

Answer 26

okay lets say it said g(f(3) I would plug in 3 into f first right?

Answer 27

If it is \(f(g(\text{insert number here}))\)

You calculate \(g(\text{insert number here})\) first, then you plug that into the greater value.

Answer 28

ohh okay I think I get it...was i right about what I said before?

Answer 29

Mindless__Unique:
okay lets say it said g(f(3) I would plug in 3 into f first right?

This?

Answer 30

yes

Answer 31

Yes, you would plug 3 into f(x) first.

Answer 32

Okay I got it now :D THANKS SO MUCH YOU GUYS YOU SAVED MY retrice

Answer 33

Watch the language lol.

Answer 34

How do I give you guys your medals?

Answer 35

lol opps

Answer 36

well, you can only give one. I can give one to whoever.

Answer 37

Thanks again guys

Answer 38

No problemo.