Increasing Function Homework: Largest Interval

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Homework Help Overview

The discussion revolves around identifying the largest interval on which the function f(x) = x² + 4x + 2 is increasing. Participants are exploring the conditions under which a function is considered increasing, particularly focusing on the derivative f'(x) and its implications.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the definitions of "increasing" versus "strictly increasing" and question whether the condition for increasing should be f'(x) > 0 or f'(x) ≥ 0. There is also consideration of different terminologies used in textbooks.

Discussion Status

There is an ongoing exploration of the appropriate conditions for determining the interval of increase. Some participants express uncertainty about the definitions and suggest verifying with external resources, such as textbooks or teachers. Multiple interpretations of the terminology are being considered.

Contextual Notes

Participants note the potential for differing definitions of increasing and non-decreasing functions across various textbooks, which may affect their understanding of the problem.

songoku
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Homework Statement


The largest interval on which the function f(x) = x2 + 4x + 2 is increasing is

a. [0, ~)
b. (-~, 0]
c. [-2, ~)
d. (-~, -2]
e. (-2, ~)

Homework Equations


differentiation

The Attempt at a Solution


I am not sure the answer is (c) or (e). The condition that the function is increasing is f '(x) > 0 or f ' (x) [tex]\geq[/tex] 0?

Thanks
 
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Hi songoku! :smile:

(have an infinity: ∞ and a geq: ≥ :wink:)
songoku said:
… The condition that the function is increasing is f '(x) > 0 or f ' (x) [tex]\geq[/tex] 0?

"increasing" means > 0; ''non-decreasing" would be ≥ 0. :wink:
 
Hi tiny-tim :smile:

Thanks a lot ! (again)
 
But there's also the distinction between "increasing" - f'(x) >= 0 and "strictly increasing" - f'(x) > 0. And similar for decreasing vs. strictly decreasing.
 
Hi Mark

Hm...so what is the appropriate condition used for this question? Thanks
 
Well, I would go with c) - [-2, inf)
 
Hm...I think I'm with you Mark :smile:
 
Songoku, the difficulty is that some textbooks use the "increasing", "nondecreasing" terminology while others use "increasing", "strictly increasing".

You ought to check with our teacher or your textbook to make sure which your class is using.
 
Hi HallsofIvy

Ok, I'll do it. Thanks a lot for your suggestion :smile:
 

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