Hey there! Sign in to join this conversationNew here? Join for free

Could somebody explain this Algebraic Operation? Watch

Announcements
    • Thread Starter
    Offline

    19
    ReputationRep:
    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
    Offline

    11
    ReputationRep:
    (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
    • Thread Starter
    Offline

    19
    ReputationRep:
    (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?
    • Community Assistant
    • Welcome Squad
    Offline

    19
    ReputationRep:
    (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.
    Offline

    11
    ReputationRep:
    (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
    Offline

    17
    ReputationRep:
    Don't know if this explains it...
    https://www.mathsisfun.com/algebra/brackets.html
    Name:  brackets.PNG
Views: 30
Size:  15.5 KB
    Offline

    11
    ReputationRep:
    (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
    Offline

    18
    ReputationRep:
    (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
    • Thread Starter
    Offline

    19
    ReputationRep:
    (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?
    Offline

    18
    ReputationRep:
    (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
    • Thread Starter
    Offline

    19
    ReputationRep:
    So does that mean the answer is -6xy - 9x + 3x^2? If not, why not?
    • Community Assistant
    • Welcome Squad
    Offline

    19
    ReputationRep:
    (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.
    • Thread Starter
    Offline

    19
    ReputationRep:
    (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
    • Community Assistant
    • Welcome Squad
    Offline

    19
    ReputationRep:
    (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.
    Offline

    20
    ReputationRep:
    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.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Break up or unrequited love?
    Useful resources

    Make your revision easier

    Maths

    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here

    Equations

    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.