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    I can't figure out where I'm going wrong here...

    If (1 + 2x)^5 + (1 - 2x)^5 = a + bx + cx^2,
    find the values of the constants a,b and c.

    I used binomial expansion and I got:
    (1 + 2x)^5 + (1 - 2x)^5 =

    1 + 10x + 40x^2 + 80x^3 + 80x^4 + 32x^5 + 1 - 10x + 40x^2 - 80x^3 + 80x^4 - 32x^5 =

    2 + 80x^2 + 160x^4

    I'm really confused...thanks in advance!
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    I agree - question seems to be wrong.
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    (Original post by Narik)
    I can't figure out where I'm going wrong here...

    If (1 + 2x)^5 + (1 - 2x)^5 = a + bx + cx^2,
    find the values of the constants a,b and c.

    I used binomial expansion and I got:
    (1 + 2x)^5 + (1 - 2x)^5 =

    1 + 10x + 40x^2 + 80x^3 + 80x^4 + 32x^5 + 1 - 10x + 40x^2 - 80x^3 + 80x^4 - 32x^5 =

    2 + 80x^2 + 160x^4

    I'm really confused...thanks in advance!
    a=2,b=0,c=80

    Edit: Your calculation is correct but the question only asks for the constant term and the coefficients of x and x^2
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    (Original post by Narik)
    I can't figure out where I'm going wrong here...

    If (1 + 2x)^5 + (1 - 2x)^5 = a + bx + cx^2,
    find the values of the constants a,b and c.

    I used binomial expansion and I got:
    (1 + 2x)^5 + (1 - 2x)^5 =

    1 + 10x + 40x^2 + 80x^3 + 80x^4 + 32x^5 + 1 - 10x + 40x^2 - 80x^3 + 80x^4 - 32x^5 =

    2 + 80x^2 + 160x^4

    I'm really confused...thanks in advance!
    your working is correct, question seems wrong
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    Just adding voice to the question being wrong in this instance.
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    Unless you square rooted, then you would have a+bx+cx^2 but I dont remember having to do anything like that in C2.
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    (Original post by mcp2)
    Unless you square rooted, then you would have a+bx+cx^2 but I dont remember having to do anything like that in C2.
    No, the square root of 2+80x^2+160x^4 isn't even a polynomial, let alone one of the form a+bx+x^2.
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    Make x^2 x, would that work?
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    (Original post by mcp2)
    Make x^2 x, would that work?
    Not really. You're getting into "2+2 = 6" if we make 2 = 3 territory. Far simpler to assume the question's wrong, to be honest.
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    (Original post by DFranklin)
    Not really. You're getting into "2+2 = 6" if we make 2 = 3 territory. Far simpler to assume the question's wrong, to be honest.
    Why is the question wrong? It asks for certain coefficients , why does it matter that the question does not ask for the coefficient of x^4
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    It doesn't ask for certain coefficients, it asks for the values of a,b,c such that (1 + 2x)^5 + (1 - 2x)^5 = a + bx + cx^2.

    There are no such values, so the question is wrong.
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    (Original post by DFranklin)
    It doesn't ask for certain coefficients, it asks for the values of a,b,c such that (1 + 2x)^5 + (1 - 2x)^5 = a + bx + cx^2.

    There are no such values, so the question is wrong.
    Thanks.
 
 
 
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