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algebra - what does this mean??

Discussion in 'Mathematics' started by chocolate_cupcake, May 11, 2011.

  1. Hello,
    Have never posted on this part of the forum but I have just had my friend call whose son is in Yr 7. He has just got really stressed over his algebra homework. One question is

    9(a+8) =

    Apparently there is nothing after the equals sign! How on earth would you do that? I haven't done algebra in years and have totally forgotten.

  2. Is the answer a = 8?

    Or am I completely wrong?!
  3. I would imagine that the child has been taught to expand brackets. Otherwise the homework seems pointless.
    However, given that you don't know how to do it, here's an example:
    4(x + 2) =
    Your job is to multiply each term (separate bit) inside the bracket by the number immediately preceding the bracket.
    So you have to do 4 times x and 4 times 2.
    This gives you 4x + 8 as your answer.
    (Extension task: if there's a minus sign in the bracket, the answer will also have a minus sign).

    cyolba, wondering if his year 11s will ever reach the dizzying heights of this level of algebraic manipulation :)
  4. Thank you cyolba! Yep I think it must be bracket expansion.

    So the answer to that would be: 9(a+8) = 9a+8?
  5. Arrrrgh LOL I mean 9a+72!!!! Not +8!!
  6. Post 5 wins the prize.
    Post 4 wins the "I posted too quickly" prize (or, in the case of the kids that I teach, the "You didn't teach it right" prize).

    cyolba, feeling wrmly positive about work today :)
  7. DM

    DM New commenter

    Are you sure?
  8. Nazard

    Nazard New commenter

    If there is also a minus sign outside the bracket then this one runs round and jumps on top of the one in the bracket to make a double-minus-sign. To the uninitiated this looks like a plus sign...
  9. Anonymous

    Anonymous New commenter

    That's a new way of explaining it. I use the two negatives come together to make the plus sign visually. No running though. It's a gentle coming together.
  10. Its possible there was an identity rather than equals sign
  11. And with some of us always
  12. I agree ResourceFinder but it is a struggle to get borderline C pupils at GCSE to comprehend the difference between an expression and equation, let alone get them to understand what an identity is. Obviously I stress the importance it with A-Level potential pupils, but it has been somewhat ignored by the GCSE boards I have used in the past but the new spec OCR GCSE seems to be very keen on the differences between Equations, Expressions, Formulae and Identities. Does it seem to be emphasised by the other boards?
  13. Even at A Level AQA do not bother with the identity sign [​IMG]

    But then they do not care about +c either (sob)

    They do care about Equations, etc though

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