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general stationary points question

Usually in Maths exams, for AQA, i find when it asks me to Differentiate a function then find the stationary points, in the mark scheme Im only supposed to take the positive value, e.g. X^2 = 4 so X = 2 but shouldn't I take the negative as well?
Check the domain of the function.
Reply 2
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Zacken
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Original post by SunDun111
Usually in Maths exams, for AQA, i find when it asks me to Differentiate a function then find the stationary points, in the mark scheme Im only supposed to take the positive value, e.g. X^2 = 4 so X = 2 but shouldn't I take the negative as well?


Post the question.
Reply 3
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Goatt
Original post by SunDun111
Usually in Maths exams, for AQA, i find when it asks me to Differentiate a function then find the stationary points, in the mark scheme Im only supposed to take the positive value, e.g. X^2 = 4 so X = 2 but shouldn't I take the negative as well?


Assuming ur talking bout shape questions, u have to take the positive value of x for obvious reasons

otherwise like big E said above check da domain

gl
Reply 4
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SunDun111
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Original post by Zacken
Post the question.


Original post by Goatt
Assuming ur talking bout shape questions, u have to take the positive value of x for obvious reasons

otherwise like big E said above check da domain

gl


dm read the question wrong thought it said x^2 = 4 it says x^1/2 = 4, but if your finding the equation of the normal at a stationary point, I think for the question X = 4 and Y = 8, wouldn't the equation by Y = 8, the mark scheme says X = 4
Original post by SunDun111
dm read the question wrong thought it said x^2 = 4 it says x^1/2 = 4, but if your finding the equation of the normal at a stationary point, I think for the question X = 4 and Y = 8, wouldn't the equation by Y = 8, the mark scheme says X = 4


..
Reply 6
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Goatt
Original post by SunDun111
dm read the question wrong thought it said x^2 = 4 it says x^1/2 = 4, but if your finding the equation of the normal at a stationary point, I think for the question X = 4 and Y = 8, wouldn't the equation by Y = 8, the mark scheme says X = 4


blud we need infoooo like the function ur working with

& this point u refer to
Reply 7
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Goatt
Original post by SunDun111
dm read the question wrong thought it said x^2 = 4 it says x^1/2 = 4, but if your finding the equation of the normal at a stationary point, I think for the question X = 4 and Y = 8, wouldn't the equation by Y = 8, the mark scheme says X = 4


What paper is it gg
Reply 8
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Zacken
22
Original post by SunDun111
dm read the question wrong thought it said x^2 = 4 it says x^1/2 = 4, but if your finding the equation of the normal at a stationary point, I think for the question X = 4 and Y = 8, wouldn't the equation by Y = 8, the mark scheme says X = 4


What does the normal look like at a stationary point? Does it look like a vertical line or a horizontal line? What does the tangent look like?
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SunDun111
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Original post by Goatt
blud we need infoooo like the function ur working with

& this point u refer to


Original post by Goatt
What paper is it gg


June 2011 , C2 diff question, Q5.
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SunDun111
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Original post by Zacken
What does the normal look like at a stationary point? Does it look like a vertical line or a horizontal line? What does the tangent look like?


Verticle... Ohhhh ok so would it be X = 4 instead?
Reply 11
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Zacken
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Original post by SunDun111
Verticle... Ohhhh ok so would it be X = 4 instead?


Yes.
Reply 12
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Goatt
Original post by SunDun111
June 2011 , C2 diff question, Q5.


[4,8] is the max that is right

What you need to do now is find the slope of the tangent at the point M then use the normal is perpendicular rule

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