# Factorise this Polynomial.Watch

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#1
Please help me factorise this polynomial. It is x3-10x2-x-30. I cannot figure out what x value will make this equal 0.
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5 years ago
#2
(Original post by VictoriaCoolio)
Please help me factorise this polynomial. It is x3-10x2-x-30. I cannot figure out what x value will make this equal 0.
Is there more to this question? It doesn't factorise very nicely.
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#3
(Original post by Serpentine111)
Is there more to this question? It doesn't factorise very nicely.
That's all my teacher gave us. She told us to try x= -2,-1,0,1,2.
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5 years ago
#4
It has a real root of 10.375, and a few complex roots as well, according to http://www.wolframalpha.com/input/?i=x3-10x2-x-30
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5 years ago
#5
(Original post by VictoriaCoolio)
Please help me factorise this polynomial. It is x3-10x2-x-30. I cannot figure out what x value will make this equal 0.
What level is this aimed at? (e.g. GCSE, A Level..)
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5 years ago
#6
(Original post by VictoriaCoolio)
Please help me factorise this polynomial. It is x3-10x2-x-30. I cannot figure out what x value will make this equal 0.
Is this meant to be trial and error?
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#7
(Original post by KingKumar)
What level is this aimed at? (e.g. GCSE, A Level..)
Further Maths, so in between A Level and GCSE.
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5 years ago
#8
(Original post by VictoriaCoolio)
Please help me factorise this polynomial. It is x3-10x2-x-30. I cannot figure out what x value will make this equal 0.
You know in further maths, at a-level you can use the calculator........the silver casio has a function where it'll tell you how to factorise up to X^3..........or you can use matlab
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5 years ago
#9
(Original post by VictoriaCoolio)
That's all my teacher gave us. She told us to try x= -2,-1,0,1,2.
Are you sure you've typed out the question correctly then?
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5 years ago
#10
The roots aren't even integers. Either the question is typed out wrong, or your teacher is giving you dodgy questions.
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#11
(Original post by Serpentine111)
Are you sure you've typed out the question correctly then?
Definately, she might have made an error, she usually does. I just typed it in on a polynomial factoring calculator and it says this:
Result
x310x2x30=x310x2x30
Explanation
x310x2x30
cannot be factored because it has no rational zeroes.
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5 years ago
#12
(Original post by VictoriaCoolio)
Definately, she might have made an error, she usually does. I just typed it in on a polynomial factoring calculator and it says this:
Result
x310x2x30=x310x2x30
Explanation
x310x2x30
cannot be factored because it has no rational zeroes.
She must've made a mistake then. There is 1 real root and 2 complex ones, but the answers aren't even integers.

In case you were interested: http://www.wolframalpha.com/input/?i=x^3-10x^2-x-30

No way is this A-level maths. I'm studying Physics at uni and I probably wouldn't be able to solve this.
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#13
(Original post by Serpentine111)
She must've made a mistake then. There is 1 real root and 2 complex ones, but the answers aren't even integers.

In case you were interested: http://www.wolframalpha.com/input/?i=x^3-10x^2-x-30

No way is this A-level maths. I'm studying Physics at uni and I probably wouldn't be able to solve this.
This is GCSE Further Maths LOL. Our teacher hates us.
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5 years ago
#14
(Original post by VictoriaCoolio)
This is GCSE Further Maths LOL. Our teacher hates us.
Hahaha, well it's definitely a mistake then.
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#15
(Original post by Serpentine111)
Hahaha, well it's definitely a mistake then.
Thanks, I will ask her tomorrow.
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5 years ago
#16
As people on this post have pointed out, there is probably an error here.

Note however, that, DOES factorise. Try the lowest 2 factors of 30 (+/-1, +/-2)- the remaining quadratic (after division/synthetic division) can be factorised by the quadratic formula. (they are conjugates that involve a surd)
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