Math Is Fun Forum

Zeeshan 01

Member

Registered: 2016-07-22

Posts: 746

Logical question

Hi I have question that when I take common from any value such that  -2xy+2y I take minus 2y common so it become -2y (x-1) now  when I take -2 common there is no minus in 2y  in original value so why we take minus common in factorization  why inside sign change??  Comm on mean that value exist in both so what this MATTER? ??

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Malik

Bob

Administrator

Registered: 2010-06-20

Posts: 10,143

Re: Logical question

-2 is not yet a factor as the 2 in the second term is + not -

But two minuses make a plus ie. -- is the same as +  so I can re-write the expression as

Now -2 and y are common factors so we can move them to a single expression outside a bracket for the remainder.

Notice I have put in an extra x 1 so that there is something in the second part of the bracket and not just an empty space or worse still a zero.

You can test whether you have factorised correctly by multiplying out:

Hope that helps.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Zeeshan 01

Member

Registered: 2016-07-22

Posts: 746

Re: Logical question

Thanks Bob you understand my question! !!!

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Malik