Author Topic: Further Maths Question method  (Read 2150 times)

Offline cashem'up

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Further Maths Question method
« on: March 30, 2011, 10:58:42 pm »
Show that the sum of the cubes of the roots of the equation
x3 + ? x + 1 = 0
is ?3.
Show also that there is no real value of ? for which the sum of the fourth powers of the roots is
negative.

ANSWER: The majority of candidates worked from S3 + ?S1 + 3 = 0
Alternatively, there were those who used the substitution X^3=Y

Now in most of these type of the questions i am only aware of the sub method... but what is the first method... can someone please explain me... the one regardin summation nd etc

elemis

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Re: Further Maths Question method
« Reply #1 on: March 31, 2011, 05:27:01 am »
What is does the question mark stand for ?

Can you rewrite the question ? Only then will I be able to answer it.

Offline cashem'up

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Re: Further Maths Question method
« Reply #2 on: March 31, 2011, 07:00:41 pm »
What is does the question mark stand for ?

Can you rewrite the question ? Only then will I be able to answer it.
? is B (a contant)
Show that the sum of the cubes of the roots of the equation
x3 + B x + 1 = 0
is minus 3.
Show also that there is no real value of B for which the sum of the fourth powers of the roots is
negative.

ANSWER: The majority of candidates worked from S3 + BS1 + 3 = 0
Alternatively, there were those who used the substitution X^3=Y

Now in most of these type of the questions i am only aware of the substitution method... but what is the first method... can someone please explain me... the one regardin summation nd etc

Offline astarmathsandphysics

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Re: Further Maths Question method
« Reply #3 on: April 01, 2011, 11:17:40 am »
When I get to pc

Offline astarmathsandphysics

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Re: Further Maths Question method
« Reply #4 on: April 02, 2011, 07:25:16 am »
1st part

Offline astarmathsandphysics

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Re: Further Maths Question method
« Reply #5 on: April 02, 2011, 07:36:33 am »
contradiction the sum of 4th powers positive see attach

Offline cashem'up

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Re: Further Maths Question method
« Reply #6 on: April 02, 2011, 01:58:22 pm »
Thanku very very much :D...cleared everything