# Finding the rAnge C3 HelpWatch

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#1
Hello,

Can anyone tell me how to find the range of y= 6/x +2x when x is greater than or equal to one but less than or equal to three? Thank you for any help!

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5 years ago
#2
(Original post by owl 1996)
Find the range of
Find and the derivative at those points: f'(1) and f'(3).

You'll find that the derivative at is less than 0 and the derivative at is greater than 0. Since the function is continuous, the derivative must be equal to 0 at a point in the interval . Find this point.

This should give you all of the information you need to sketch the graph.

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(Original post by m4ths/maths247)
What techniques do you think you could use? (you have a small interval there too which may help....)
Do you think I've given too much of the question away? I haven't explicitly calculated anything but I have outlined most if not all of the method.
0
5 years ago
#3
(Original post by owl 1996)
Hello,

Can anyone tell me how to find the range of y= 6/x +2x when x is greater than or equal to one but less than or equal to three? Thank you for any help!

Posted from TSR Mobile
What techniques do you think you could use? (you have a small interval there too which may help....)
0
#4
(Original post by Khallil)
Find and the derivative at those points: f'(1) and f'(3).

You'll find that the derivative at is less than 0 and the derivative at is greater than 0. Since the function is continuous, the derivative must be equal to 0 at a point in the interval . Find this point.

This should give you all of the information you need to sketch the graph.

Spoiler:
Show
Do you think I've given too much of the question away? I haven't explicitly calculated anything but I have outlined most if not all of the method.
The lowest f(x) can be is 4*3^(1/2) . Thank you!

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#5
(Original post by m4ths/maths247)
What techniques do you think you could use? (you have a small interval there too which may help....)
Thanks

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0
5 years ago
#6
(Original post by owl 1996)
The lowest f(x) can be is 4*3^(1/2) . Thank you!

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Now you can find the greatest value can take and that gives you the range.

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