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# Can anyone explain this factorising answer for me? watch

1. Hi
I've just started teaching myself AS Maths and I've had no problem with factorising until this particular question came up in my textbook (CGP Edexcel C1):

2(2x-y)² -6x(2x-y)

Answer in back of textbook is
=2(2x-y)[(2x-y)-3x]
= -2(2x-y)(x+y)

I'm just not understanding how to arrive at the second line of the answer... Hopefully it's something simple and I'm just having a blonde moment! Thanks if you can help to explain.

Kim
2. (Original post by kimbo8672)
Hi
I've just started teaching myself AS Maths and I've had no problem with factorising until this particular question came up in my textbook (CGP Edexcel C1):

2(2x-y)² -6x(2x-y)

Answer in back of textbook is
=2(2x-y)[(2x-y)-3x]
= -2(2x-y)(x+y)

I'm just not understanding how to arrive at the second line of the answer... Hopefully it's something simple and I'm just having a blonde moment! Thanks if you can help to explain.

Kim
3. Look at both terms in the original equation, what do they have in common?
4. wait a sec i'm writing an answer
5. (Original post by kimbo8672)
Hi
I've just started teaching myself AS Maths and I've had no problem with factorising until this particular question came up in my textbook (CGP Edexcel C1):

2(2x-y)² -6x(2x-y)

Answer in back of textbook is
=2(2x-y)[(2x-y)-3x]
= -2(2x-y)(x+y)

I'm just not understanding how to arrive at the second line of the answer... Hopefully it's something simple and I'm just having a blonde moment! Thanks if you can help to explain.

Kim
i don't know wtf they've done there with that, i can't seem to make any sense out of it but here's an alternative if you want

6. (Original post by thefatone)
i don't know wtf they've done there with that, i can't seem to make any sense out of it but here's an alternative if you want
Full solutions are against forum guidelines.

...not to mention that your method is exceedingly convoluted and highly unnecessary.
7. (Original post by kimbo8672)
Hi
I've just started teaching myself AS Maths and I've had no problem with factorising until this particular question came up in my textbook (CGP Edexcel C1):

2(2x-y)² -6x(2x-y)

Answer in back of textbook is
=2(2x-y)[(2x-y)-3x]
= -2(2x-y)(x+y)

I'm just not understanding how to arrive at the second line of the answer... Hopefully it's something simple and I'm just having a blonde moment! Thanks if you can help to explain.

Kim
Ignore the poster who gave you the full solution (albeit long winded one).

Look at both terms of your equation, we have being a common factor. It might help if we call , so that we can write your equation as:

Now, I assume that you've gotten this far. Notice that
8. (Original post by Zacken)
Full solutions are against forum guidelines.

...not to mention that your method is exceedingly convoluted and highly unnecessary.
They're against guidelines?
9. (Original post by thefatone)
They're against guidelines?
Yep. It's much better to give hints and teach the user than just blindly giving them the full solution.
10. (Original post by Zacken)
Yep. It's much better to give hints and teach the user than just blindly giving them the full solution.
Oh i see....
11. Thanks everyone for replying, but I'm still not fully getting it... Maybe I will come back to it in a few minutes. Feeling brain dead!
12. (Original post by kimbo8672)
Thanks everyone for replying, but I'm still not fully getting it... Maybe I will come back to it in a few minutes. Feeling brain dead!
Okay, what part don't you understand? Work with us here.

Do you get that ?
13. I think ive got it now, thank you! I just didnt know that making the inital 2 a negative would be the thing to do. Lesson learned! Cheers!
14. (Original post by kimbo8672)
I think ive got it now, thank you! I just didnt know that making the inital 2 a negative would be the thing to do. Lesson learned! Cheers!
Great!
15. (Original post by Zacken)
Okay, what part don't you understand? Work with us here.

Do you get that ?
Yes, thank you. It was putting this negative into the whole answer that was throwing me.

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Updated: February 14, 2016
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