Tell me where I messed up ?
f(x)=-4x-1 when f(x) is -2
f(-2)=-4(-2)-1
f=-4(-2)-1+2
f=8-1+2
f=7+2
f=9
But -9 is an answer . :/

- anonymous

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- Luigi0210

Uh, you messed up on the third step

- Luigi0210

Where did that +2 come from?

- anonymous

the f(-2) is just like saying "y, when x=-2"

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## More answers

- anonymous

But ..

- anonymous

I dont understand .

- Nurali

f(x)=-4x-1 when f(x) is -2
f(-2)=-4(-2)-1
f(-2)=8-1
f(-2)=7

- anonymous

So you dont move the -2 on the left side ? :/

- anonymous

\[f(-2)=-4(-2)-1\]\[f(-2)=8-1\]\[f=7\]

- Luigi0210

There is no -2 on the left

- anonymous

F(-2) is what someone else said .

- Luigi0210

It's just saying that you plug in -2 where ever there is an x

- anonymous

Yeah & I thought you had to isolate F .

- anonymous

f(x) means the function of x
f(-2) means the function when x is -2
bascially f(anything) is like saying 'y'
the only reason it is written as f(-2) is so that we know that they want "the value of the FUCNTION when X is" -2

- DebbieG

Noooooo......
f(x)=-4x-1 when f(x) is -2 means
-2=-4x-1

- anonymous

f(x) is f sub x .

- Luigi0210

@DebbieG no, you must be thinking of substitution or something

- DebbieG

It says WHEN F(X) IS -2.
That isn't when x=2, it's when f(x)=-2

- anonymous

oh wait....debbie's right
they want the value of x when f(x) is -2
\[f(x)=-4x-1\]\[-2=-4x-1\]

- Luigi0210

Wait.. darn it

- DebbieG

@Sceenie , is 1/4 by chance an answer?

- anonymous

@Luigi0210 it says when f(x) is -2, not f(-2)

- DebbieG

<--- what she said. :P

- Luigi0210

Hey, you made the same mistake yummy xD

- anonymous

No , It's not . The answers are
-9
-7
-10
7

- anonymous

yea i know, i think we got caught up with the fact that she completely misunderstood f(x)

- DebbieG

Well, that's interesting. Is that the whole question up above? Exactly as you have it?

- anonymous

*smack* I hate math . xD

- Luigi0210

Well if we did need to plug in -2 for x, the answer would of been -7

- Luigi0210

Which is a choice

- DebbieG

DON'T HATE ON THE MATH! :)

- anonymous

If f(x) = −4x − 1, find f(−2).

- anonymous

Yes then what we explained is correct and the answer is -7

- DebbieG

ah HA! that's different than what you posted above! :) lol

- anonymous

Hah, @Luigi0210 we were right! :D

- Luigi0210

Yay!

- DebbieG

(And has a very different meaning. :)

- anonymous

^yes

- Luigi0210

Next time write it word for word

- anonymous

*cries internally* I thought it was substitution .

- Luigi0210

Don't re-word or anything

- anonymous

you are substituting....substituting -2 for x

- anonymous

I didnt reword , i typed what I had written on my paper.

- DebbieG

's ok.... it's instructive and useful to see what a huge difference that slight change in the language makes! :) And we got to the bottom of it, so all is well. :)

- anonymous

Just, whoever taught you functions didnt do a great job at explaining the concept of f(x)

- Luigi0210

^

- anonymous

< Wasnt taught how to do it .

- anonymous

did you skip a level of math?

- anonymous

So is it 7 ?

- anonymous

i mean Seven lol sorry

- anonymous

DONT YELL .

- DebbieG

But
\(\Large \text{f(x)=-4x-1 when f(x) is -2}\)
is different from
\(\Large \text {If f(x) = −4x − 1, find f(−2).}\)
Do you see the difference?

- Luigi0210

Who's yelling?

- anonymous

Yes & Thank you , Debbie .c:

- anonymous

Anyway, we're all grown ups here (I'd like to think)
the situation is handeled, just make sure next time you type exactly what the question asks because now you see how the slightest difference changes the whole question.

- DebbieG

You're welcome. :) I always say, "math is a precise science!" :) Little differences make a big difference sometimes, lol. :)

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