Could somebody explain this Algebraic Operation?

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    Hi,

    The question:

    -[3x - (2y + 3) - 3x^2] = ?

    The answer I have is 6xy + 9x - 3x^2. But, I suspect this is incorrect because I'm not entirely sure what the '[ ]' brackets mean in Maths. So, for instance, is the - (2y...' part equivalent to -2y?

    Any help would be appreciated!

    Thanks
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    (Original post by Exceptional)
    Hi,

    The question:

    -[3x - (2y + 3) - 3x^2] = ?

    The answer I have is 6xy + 9x - 3x^2. But, I suspect this is incorrect because I'm not entirely sure what the '[ ]' brackets mean in Maths. So, for instance, is the - (2y...' part equivalent to -2y?

    Any help would be appreciated!

    Thanks
    first do this part "-(2y + 3)" = -2y - 3

    then multiply each term by - 1 which is the "-[ ]" part
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    (Original post by KINGYusuf)
    first do this part "-(2y + 3)" = -2y - 3

    then multiply each term by - 1 which is the "-[ ]" part
    Thanks. Could you explain why -(2y + 3) becomes -2y - 3? And, why does '-[ ]' mean multiply each term by -1?
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    (Original post by Exceptional)
    Thanks. Could you explain why -(2y + 3) becomes -2y - 3? And, why does '-[ ]' mean multiply each term by -1?
    It's basic multiplicative distribution. The square brackets are no different from normal brackets as far as operations of arithmetic are concerned.
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    (Original post by Exceptional)
    Thanks. Could you explain why -(2y + 3) becomes -2y - 3? And, why does '-[ ]' mean multiply each term by -1?
    so think of it like this:

    -( ) means -1 x each term inside the bracket

    same for -[ ] it means -1 x each term inside the bracket
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    Don't know if this explains it...
    https://www.mathsisfun.com/algebra/brackets.html
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    (Original post by Exceptional)
    Thanks. Could you explain why -(2y + 3) becomes -2y - 3? And, why does '-[ ]' mean multiply each term by -1?
    imagine you had -2(2y + 3)

    you multiply -2 x everything inside the bracket right?

    well -(2y+3) you multiply each term inside the bracket by -1,

    the "1" just isn't written
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    (Original post by Exceptional)
    Hi,

    The question:

    -[3x - (2y + 3) - 3x^2] = ?

    The answer I have is 6xy + 9x - 3x^2. But, I suspect this is incorrect because I'm not entirely sure what the '[ ]' brackets mean in Maths. So, for instance, is the - (2y...' part equivalent to -2y?

    Any help would be appreciated!

    Thanks
    in this equation, the [ ] brackets basically say that the WHOLE equations is negative
    so basically
    -3x + (2y+3) + 3x2

    check with someone else though, i might be wring
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    (Original post by animeamanda1412)
    in this equation, the [ ] brackets basically say that the WHOLE equations is negative
    so basically
    -3x + (2y+3) + 3x2

    check with someone else though, i might be wring
    That makes sense - do I need to expand the bracket to reach the answer?
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    (Original post by Exceptional)
    That makes sense - do I need to expand the bracket to reach the answer?
    I'd say if you're really confident with these type of questions then you don't have to, but I always expand, better than working the whole thing out then realise you have to do eeverythingggg again because of a mistake in the signs
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    So does that mean the answer is -6xy - 9x + 3x^2? If not, why not?
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    (Original post by Exceptional)
    So does that mean the answer is -6xy - 9x + 3x^2? If not, why not?
    It's not. Why not, you may ask?? Well that's hard to say when I don't know where you went wrong. For example, there is no xy term so I don't know where you got that from in the first place. Just expand the normal brackets inside first, then the square bracket as a whole.
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    (Original post by RDKGames)
    It's not. Why not, you may ask?? Well that's hard to say when I don't know where you went wrong. For example, there is no xy term so I don't know where you got that from in the first place. Just expand the normal brackets inside first, then the square bracket as a whole.
    The same way Reality Check got it in the post before yours
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    (Original post by Reality Check)
    you need to multiply the terms in the round brackets by -1

    -[3x-(2y+3)-3x^2] = -[3x(-2y-3)-3x^2]
    (Original post by Exceptional)
    The same way Reality Check got it in the post before yours
    Er, no, you distribute the -1 and it becomes a +1, it doesn't just magically disappear and you multiply two things all of a sudden.
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    First, multiply the round brackets by -1:

    -[3x -(2y+3)-3x^2 = -[3x - 2y -3 - 3x^2]

    Then multiply everything by -1 outside the square brackets:

    -3x + 2y +9 + 3x^2

    Then factorise where possible:

    2y -3(x -x^2 -3)

    I hope that's right but I'm perfectly open to being politely corrected! By the way, you haven't said what you're solving for.
 
 
 
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