anonymous
  • anonymous
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 . :/
Mathematics
  • Stacey Warren - Expert brainly.com
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SOLVED
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jamiebookeater
  • jamiebookeater
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Luigi0210
  • Luigi0210
Uh, you messed up on the third step
Luigi0210
  • Luigi0210
Where did that +2 come from?
anonymous
  • anonymous
the f(-2) is just like saying "y, when x=-2"

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anonymous
  • anonymous
But ..
anonymous
  • anonymous
I dont understand .
Nurali
  • Nurali
f(x)=-4x-1 when f(x) is -2 f(-2)=-4(-2)-1 f(-2)=8-1 f(-2)=7
anonymous
  • anonymous
So you dont move the -2 on the left side ? :/
anonymous
  • anonymous
\[f(-2)=-4(-2)-1\]\[f(-2)=8-1\]\[f=7\]
Luigi0210
  • Luigi0210
There is no -2 on the left
anonymous
  • anonymous
F(-2) is what someone else said .
Luigi0210
  • Luigi0210
It's just saying that you plug in -2 where ever there is an x
anonymous
  • anonymous
Yeah & I thought you had to isolate F .
anonymous
  • 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
  • DebbieG
Noooooo...... f(x)=-4x-1 when f(x) is -2 means -2=-4x-1
anonymous
  • anonymous
f(x) is f sub x .
Luigi0210
  • Luigi0210
@DebbieG no, you must be thinking of substitution or something
DebbieG
  • DebbieG
It says WHEN F(X) IS -2. That isn't when x=2, it's when f(x)=-2
anonymous
  • 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
  • Luigi0210
Wait.. darn it
DebbieG
  • DebbieG
@Sceenie , is 1/4 by chance an answer?
anonymous
  • anonymous
@Luigi0210 it says when f(x) is -2, not f(-2)
DebbieG
  • DebbieG
<--- what she said. :P
Luigi0210
  • Luigi0210
Hey, you made the same mistake yummy xD
anonymous
  • anonymous
No , It's not . The answers are -9 -7 -10 7
anonymous
  • anonymous
yea i know, i think we got caught up with the fact that she completely misunderstood f(x)
DebbieG
  • DebbieG
Well, that's interesting. Is that the whole question up above? Exactly as you have it?
anonymous
  • anonymous
*smack* I hate math . xD
Luigi0210
  • Luigi0210
Well if we did need to plug in -2 for x, the answer would of been -7
Luigi0210
  • Luigi0210
Which is a choice
DebbieG
  • DebbieG
DON'T HATE ON THE MATH! :)
anonymous
  • anonymous
If f(x) = −4x − 1, find f(−2).
anonymous
  • anonymous
Yes then what we explained is correct and the answer is -7
DebbieG
  • DebbieG
ah HA! that's different than what you posted above! :) lol
anonymous
  • anonymous
Hah, @Luigi0210 we were right! :D
Luigi0210
  • Luigi0210
Yay!
DebbieG
  • DebbieG
(And has a very different meaning. :)
anonymous
  • anonymous
^yes
Luigi0210
  • Luigi0210
Next time write it word for word
anonymous
  • anonymous
*cries internally* I thought it was substitution .
Luigi0210
  • Luigi0210
Don't re-word or anything
anonymous
  • anonymous
you are substituting....substituting -2 for x
anonymous
  • anonymous
I didnt reword , i typed what I had written on my paper.
DebbieG
  • 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
  • anonymous
Just, whoever taught you functions didnt do a great job at explaining the concept of f(x)
Luigi0210
  • Luigi0210
^
anonymous
  • anonymous
< Wasnt taught how to do it .
anonymous
  • anonymous
did you skip a level of math?
anonymous
  • anonymous
So is it 7 ?
anonymous
  • anonymous
i mean Seven lol sorry
anonymous
  • anonymous
DONT YELL .
DebbieG
  • 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
  • Luigi0210
Who's yelling?
anonymous
  • anonymous
Yes & Thank you , Debbie .c:
anonymous
  • 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
  • DebbieG
You're welcome. :) I always say, "math is a precise science!" :) Little differences make a big difference sometimes, lol. :)

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