Thread: Math Question

  1. #1

    Math Question

    So, I've got the next 8 months to revise for my maths module. I'm doing a degree in Computer Science and I need to brush up on my Math. Been smooth sailing so far, but I've hit a stumbling block. I know the anwser to the below question, but I cannot get to it. The divide line in the middle is really messing me up.

    D = 3a^2 + 2B
    ------------
    4 (c + 3)

    a = -2
    b = 2
    c = -4


    If you could walk through this with me, with the correct answer, it would be much appreciated. I know it's not too difficult, but when you haven't done anything like this for nearly 10 years, it's fairly difficult to remember. I know my BODMAS (Brackets, Other, Divide, Multiply, Add, Subtract), but this one is really doing my head in!

  2. #2
    Code:
    D	=	(3a^2 + 2b) / (4(c + 3))
    D	=	(3*-2^2 + 2*2) / (4(-4 + 3))
    D	=	(3*4 + 4) / (4*-1)
    D	=	(12 + 4) / -4
    D	=	16 / -4
    D	=	-4
    Maybe I'm missing something, but that's what we came up with.

  3. #3
    Quote Originally Posted by Ragedaug View Post
    Code:
    D	=	(3a^2 + 2b) / (4(c + 3))
    D	=	(3*-2^2 + 2*2) / (4(-4 + 3))
    D	=	(3*4 + 4) / (4*-1)
    D	=	(12 + 4) / -4
    D	=	16 / -4
    D	=	-4
    Maybe I'm missing something, but that's what we came up with.
    You're correct, but I thought that a positive * negative = negative?

  4. #4
    Quote Originally Posted by Kings Road View Post
    You're correct, but I thought that a positive * negative = negative?
    it's -2^2 a negative squared is a positive

    so 3*-2^2 = 3*(-2)^2 (you must use the bracket around the the - if you use calculator) = 3*4 =12

  5. #5
    Yes king's, however in this case it is 3 * 4 because the a is squared meaning:
    3 * (-2)^2
    = 3 * (-2 * -2)
    = 3 * 4 = 12.

  6. #6
    Quote Originally Posted by Kjanaprik View Post
    it's -2^2 a negative squared is a positive

    so 3*-2^2 = 3*(-2)^2 (you must use the bracket around the the - if you use calculator) = 3*4 =12
    Boom.
    Thank you.
    I got my answer and I see clearly how I got there.

    Thanks to both of you!

  7. #7
    Please Excuse My Dear Aunt Sally

    There is an order of operations: P = Parenthesis, E = Exponentiation, M/D = Mult/Divide, A/S = Add/Subtract

    Exponentiation comes before multiplication, so you have to make -2^2 = 4 before you even consider multiplying by 3.

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