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    x^2/3 - x^1/3 - 6 = 0

    I tried to solve it but got X^2 - X -216 = 0 which i couldn't solve so i assume thats completely wrong. Am i the only one who struggled here?
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    (Original post by EpicnessNinjaa)
    x^2/3 - x^1/3 - 6 = 0

    I tried to solve it but got X^2 - X -216 = 0 which i couldn't solve so i assume thats completely wrong. Am i the only one who struggled here?
    You were supposed to use the substition of k=x^1/3 and you'd be able to factories, find k and then cube it to find your values of x. Should have gotten -8 and 27
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    (Original post by EpicnessNinjaa)
    x^2/3 - x^1/3 - 6 = 0

    I tried to solve it but got X^2 - X -216 = 0 which i couldn't solve so i assume thats completely wrong. Am i the only one who struggled here?
    This is a sneaky disguised quadratic:

    x^\frac{2}{3} - x^\frac{1}{3} - 6 = (x^\frac{1}{3})^2 - x^\frac{1}{3} - 6
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    (Original post by lizard54142)
    This is a sneaky disguised quadratic:

    x^\frac{2}{3} - x^\frac{1}{3} - 6 = (x^\frac{1}{3})^2 - x^\frac{1}{3} - 6
    If you look at the previous mark schemes for these kind of questions, they want you to specifically use substitution of some sorts. It's said before that if you factorise it immediately, you don't get method marks
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    (Original post by ChoccyPhilly)
    If you look at the envious mark schemes for these kind of questions, they want you to specifically use substitution of some sorts. It's said before that if you factorise it immediately, you don't get method marks
    Why? It shows that you can deal directly with fractional indices. I don't believe this.
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    (Original post by lizard54142)
    Why? It shows that you can deal directly with fractional indices. I don't believe this.
    http://www.ocr.org.uk/Images/58512-m...ics-1-june.pdf

    Question 6

    "No marks unless evidence of substituion"

    I know, I couldn't believe it either too but it's because they want you to use specific techniques.
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    (Original post by ChoccyPhilly)
    http://www.ocr.org.uk/Images/58512-m...ics-1-june.pdf

    Question 6

    "No marks unless evidence of substituion"

    I know, I couldn't believe it either too but it's because they want you to use specific techniques.
    Use a substitution to obtain a quadratic or factorise into 2 brackets each containing x^\frac{1}{4}

    So they should give you the mark. Although there is conflicting information in the far right column, "no marks unless evidence of substitution (quadraticseen or square rooting or squaring of roots found).= 0 may be implied". Not too sure, it's a poor mark scheme.

    If you wouldn't get the mark then that is disgraceful.
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    (Original post by lizard54142)
    Use a substitution to obtain a quadratic or factorise into 2 brackets each containing x^\frac{1}{4}

    So they should give you the mark. Although there is conflicting information in the far right column, "no marks unless evidence of substitution (quadraticseen or square rooting or squaring of roots found).= 0 may be implied". Not too sure, it's a poor mark scheme.

    If you wouldn't get the mark then that is disgraceful.
    When I did my core1 mock,I had a question like this and my teacher didn't give me any marks due to not substituting, so I base it off that. At worst, youd probably only lose 2 marks
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    (Original post by ChoccyPhilly)
    When I did my core1 mock,I had a question like this and my teacher didn't give me any marks due to not substituting, so I base it off that. At worst, youd probably only lose 2 marks
    Losing any marks at all would be a joke.
 
 
 
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