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# Could somebody explain this Algebraic Operation?

1. 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
2. (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
3. (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?
4. (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.
5. (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
6. Don't know if this explains it...
https://www.mathsisfun.com/algebra/brackets.html
7. (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
8. (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
9. (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?
10. (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
11. So does that mean the answer is -6xy - 9x + 3x^2? If not, why not?
12. (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 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.
13. (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 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
14. (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.
15. 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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