Can't understand factorising by taking out common factors

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Crob11258
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#1
Report Thread starter 7 years ago
#1
I can do the easier ones (e.g 3x-6) it's when I see questions such as (2t+s)(2t-s)+(2t-s) I just don't know how to do them!



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Kvothe the Arcane
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#2
Report 7 years ago
#2
(Original post by Crob11258)
I can do the easier ones (e.g 3x-6) it's when I see questions such as (2t+s)(2t-s)+(2t-s) I just don't know how to do them!



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What do you find hard about the latter example?
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Bloxorus
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(Original post by Crob11258)
I can do the easier ones (e.g 3x-6) it's when I see questions such as (2t+s)(2t-s)+(2t-s) I just don't know how to do them!



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The latter example is exactly the same as the first. Ask yourself what factors occupy both parts of the function and then take them out.
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Mr M
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#4
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#4
(Original post by Crob11258)
when I see questions such as (2t+s)(2t-s)+(2t-s) I just don't know how to do them!
Just look at both terms and see what they have in common. In this case they both have a factor of (2t-s).

(2t+s)(2t-s)+(2t-s)=(2t-s)(2t+s+1)
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sarahwaymouth
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#5
[QUOTE=Crob11258;46680103]I can do the easier ones (e.g 3x-6) it's when I see questions such as (2t+s)(2t-s)+(2t-s) I just don't know how to do them!

I'm going to try explain it as simply as poss

With 3x-6, you split into 2 parts, "3x" and "-6" find a common factor (3) and factorise.

Do exactly the same with (2t+s)(2t-s)+(2t-s), split to get "(2t+s)(2t-s)" and "1 X (2t-s)", it is clear that (2t-s) is a factor you can take out of both, which leaves you with (2t+s) and 1, = 2t+s+1

ANSWER= Factor X what is left over
=(2t-s)(2t+s+1)
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krisshP
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#6
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#6
Maybe it helps if you view it like this.

Remember t and a are just unknowns, so 2t+s as well as 2t-s are just numbers. So it may be like this where 2t+s=5 and 2t-s=3

(2t+s)(2t-s)+(2t-s)
=(5)(3)+3
=3(5+1)
=(2t-s)[(2t+s)+1]

Then you could expand if you want to, but I hope that illustrates my point that you just treat (2t+s) and (2t-s) like ordinary numbers, as after all that's what they are, but with unknowns in them which seem to make it look harder.
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