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Evaluating Polynomial Function

evking

New member
Joined
Aug 30, 2017
Messages
13
The question is f(x[SUP]2[/SUP])=-x[SUP]2[/SUP]+5x-2 So I plugged in the X[SUP]2[/SUP] as X and got -x[SUP]4[/SUP]+5x[SUP]2[/SUP]-2 but the multiple choice only has -4[SUP]​4[/SUP]+x[SUP]2[/SUP]-2, and if the multiple choice is correct what happened to the 5?
 
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Bob Brown MSEE

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Oct 25, 2012
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594
What's the question?

The question is f(x[SUP]2[/SUP])=-x[SUP]2[/SUP]+5x-2 So I plugged in the X[SUP]2[/SUP] as X and got -x[SUP]4[/SUP]+5x[SUP]2[/SUP]-2 but the multiple choice only has -4[SUP]​4[/SUP]+x[SUP]2[/SUP]-2, and if the multiple choice is correct what happened to the 5?
It helps us if you give us the problem exactly as it was written when you got it.

Was the question, "What is f(x)?" ?
Was one choice, "-x + 5Sqrt[x] -2" ?
 

evking

New member
Joined
Aug 30, 2017
Messages
13
It helps us if you give us the problem exactly as it was written when you got it.

Was the question, "What is f(x)?" ?
Was one choice, "-x + 5Sqrt[x] -2" ?
The question says " Polynomial Functions are shown below, plug in the following values as X to get the output values."
I know for sure that -x[SUP]4[/SUP]+x[SUP]2[/SUP]-2 is the answer that is considered correct for that problem because it was graded as correct I am just curious why it is considered correct instead of -x[SUP]4[/SUP]+5x[SUP]​2[/SUP]-2. Hope that helps.
 

Ishuda

Elite Member
Joined
Jul 30, 2014
Messages
3,345
The question says " Polynomial Functions are shown below, plug in the following values as X to get the output values."
I know for sure that -x[SUP]4[/SUP]+x[SUP]2[/SUP]-2 is the answer that is considered correct for that problem because it was graded as correct I am just curious why it is considered correct instead of -x[SUP]4[/SUP]+5x[SUP]​2[/SUP]-2. Hope that helps.


As a spin off from Bob Brown's post:
Two things:
(1) Is the original polynomial
f(x) = -x[SUP]2[/SUP]+5x-2
so that, in reality,
f(x[SUP]2[/SUP]) = -x[SUP]4[/SUP]+5x[SUP]2[/SUP]-2

(2) If that is the original polynomial 'printed in the book' it looks like maybe a typo and it should have been
f(x) = -x[SUP]2[/SUP]+x-2
so that
f(x[SUP]2[/SUP]) = -x[SUP]4[/SUP]+x[SUP]2[/SUP]-2
 
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