The Student Room Group

Minimum Point On A Curve

how to find the minimum point of a curve. I know you have to complete the square but i dont understand how you find the minimum points.

E.g. - 8x + 23 = (x-a)² + b
(x-4)² + 7 = 0

so what would the minimum points be and how would you work it out

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Reply 1
Find the second derivitive, and the higher value is the min
Reply 2
can you give a gcse answer plss
Reply 3
Rudeboy999
how to find the minimum point of a curve. I know you have to complete the square but i dont understand how you find the minimum points.

E.g. - 8x + 23 = (x-a)² + b
(x-4)² + 7 = 0

so what would the minimum points be and how would you work it out

The minimum point will be when x = -4. You have to set the inside of the bracket to zero.

Sub x= -4 in to the original equation to find the value of the function at this point.

source: http://www.mathcentre.ac.uk/resources/workbooks/mathcentre/web-completingsquare1.pdf (section 4)
Reply 4
You don't need to know that at gcse???
differentiate it and then put in 'o' as the dy/dx.
Reply 6
jklmn
You don't need to know that at gcse???


englishman129
differentiate it and then put in 'o' as the dy/dx.


He is a GCSE student. Calculus is obviously not part of the GCSE syllabus. Stop trying to look clever guys - you're just looking like idiots by not reading the original question.
okay, sorry - i'm doing GCSE Additional maths - where calculus is REQUIRED, i've never done it in normal maths. So u do diffrentiate.
englishman129
okay, sorry - i'm doing GCSE Additional maths - where calculus is REQUIRED, i've never done it in normal maths. So u do diffrentiate.

Differentiate, set this equal to 0 to find stationary points.

Check values either side of any stationary points to see whether they are minimum or maximum
jonny23563
Differentiate, set this equal to 0 to find stationary points.

Check values either side of any stationary points to see whether they are minimum or maximum


exactly.
Reply 10
englishman129
okay, sorry - i'm doing GCSE Additional maths - where calculus is REQUIRED, i've never done it in normal maths. So u do diffrentiate.


For this question, you can get the answer much more easily without calculus (although it would work too, it's just waaay longer)

It helps to imagine the curve, and the lowest point on that curve will be y=7 (due to the translation of the curve)
You can sub this value for y into the equation, and end up with a value for x
It is much faster/easier than calculus.

Edit: how many marks for this question? If it's just one or two, they won't be expecting you to differentiate.
Reply 11
this is at gcse level btw
assmaster
For this question, you can get the answer much more easily without calculus (although it would work too, it's just waaay longer)

It helps to imagine the curve, and the lowest point on that curve will be y=7 (due to the translation of the curve)
You can sub this value for y into the equation, and end up with a value for x
It is much faster/easier than calculus.

Edit: how many marks for this question? If it's just one or two, they won't be expecting you to differentiate.


BTW i'm not asking the question...i just responded saying you have to differentiate and i know how to do it. It's the original poster who dosen't lol - everyone keeps quoting me.
Rudeboy999
this is at gcse level btw


dude, i've never covered it in my normal maths syllabus, do you even have to?
Reply 14
englishman129
BTW i'm not asking the question...i just responded saying you have to differentiate and i know how to do it. It's the original poster who dosen't lol - everyone keeps quoting me.


I know sweetie, the OP will be watching the thread and will hopefully read what I said... :rolleyes:
Also you don't have "Thread Starter" under your username :yep:
Reply 15
This is a GCSE level, although A* stuff :smile:. The answer is right there after youcomplete the square.
Reply 16
assmaster
I know sweetie, the OP will be watching the thread and will hopefully read what I said... :rolleyes:
Also you don't have "Thread Starter" under your username :yep:

You never call me sweetie, yet this scrot gets it? :frown:

*cries*
Lol :smile:
M_E_X
You never call me sweetie, yet this scrot gets it? :frown:

*cries*


awwwwww how upsetting :frown:, i duno wot i even done to annoy you lol :s-smilie:
Reply 19
M_E_X
You never call me sweetie, yet this scrot gets it? :frown:

*cries*


Cutie?

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