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Karen L.

asked • 03/28/14

functions and formulas

help me translate this into english please!!
f(x)=4x^+2;find f(-1) what is this asking? i know that f(x) is the same as y,correct? what do they mean by "find f(-1) are they asking to find x and y?

3 Answers By Expert Tutors

By:

Karen L.

Then I was on the right track! y=fx I wrote the equation as f(-1) = -4(-1^)+2 ...so y ==2 and x=-1???
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03/29/14

Jim S.

tutor
Yes
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03/29/14

Stephen W.

tutor
Here are a few results when f(x)=4x2
 
When x=-1, y=4.
When x=0, y=0.
When x=1, y=4.
When x=2, y=16.
 
I don't know what you guys are talking about right now. If you get time, do you mind posting again to explain? I get the feeling that the original problem was displayed incorrectly, or something like that.
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03/29/14

Jim S.

tutor
Steve,
          The syntax of some of the problems that are posted leaves a lot to be desired. When I have a question about where the () should be I usually try and figure out from the context how the problem might make sense and proceed accordingly.
The original problem as posted is: "help me translate this into english please!!
f(x)=4x^+2;find f(-1) what is this asking? i know that f(x) is the same as y,correct? what do they mean by "find f(-1) are they asking to find x and y?"
I just assumed that f(x) =4x2 …..
 
Jim
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03/29/14

Stephen W.

tutor
Thanks, Jim. I understand that much. It is when I get to "f(-1) = -4(-1^)+2 ...so y ==2 and x=-1" that it stops making sense to me. I interpreted this to be:
f(-1) = 4(-1)2, with y=2 when x=-1, which is not correct, of course. 
Thanks for trying to explain.
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03/29/14

Steve S. answered • 03/29/14

Tutor
5 (3)

Tutoring in Precalculus, Trig, and Differential Calculus

Karen L.

Where do you get the 18? I am totally confused..I get that you substitute the x for -1
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03/29/14

Karen L.

Steve,Dont get the 4(18) you have an extra 2 in there..the original equation is:y(x)=-4x^+2;asking to find -1..(the x is squared...)
so if you say i substute a-1 where ever there is an x...then f(-1)= -4(-1^)+2,yes?...that would be -4(1) or -4 +2 which equals -2...
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03/29/14

Karen L.

Its a -4
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03/29/14

Stephen W.

tutor
That's right Karen. Thanks for the catch! I will fix it. The 18 was an example. There has been some discussion among the tutors about using the actual problem, in case it is for homework, so I was attempting to provide an alternative. The +2 was a mistake. Thanks, Karen from Fremont NH!
 
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03/29/14

Karen L.

No problem..thanks for the response and help.
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03/30/14

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