Plzz tell the reason of this answer that why, there is (2s-1) why not (2s+1) where i have done a circle .plzz tell the right answer and i will mark as brainliest and i will follow you. IF YOU WILL GIVE RUBBISH ANSWERS I WILL REPORT YOUR ANSWER.
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Essentially, it's the "negative by negative is positive" thing.
Consider expanding the last term, using the fact that a(b+c) = ab+ac :
- ( 2s - 1 )
= (-1) × ( 2s + (-1) )
= (-1) × 2s + (-1) × (-1)
= -2s + 1
which matches the two last terms on the previous line.
If instead you put (2s+1) there, that would be
- ( 2s + 1 )
= (-1) × ( 2s + 1 )
= (-1) × 2s + (-1) × 1
= -2s - 1.
Do watch out for grouping when there are minus signs involved. It's easy to make mistakes! The patterns that you see are things like:
- + a + b = + ( a + b )
- + a - b = + ( a - b )
- - a + b = - ( a - b )
- - a - b = - ( a + b )
So all together
4s² - 2s - 2s + 1
= ( 4s² - 2s ) - ( 2s - 1 )
= 2s ( 2s - 1 ) - ( 2s - 1 )
= ( 2s - 1 )²
Hope this helps you out.
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