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# Need help with GCSE question watch

1. Show that
x²-(x-1)²=2x-1

Show me how please? Also can someone tell me what this is called so I can revise it more, thanks.
2. multiply out the brackets you will end up with x² minus x² so they cancel out and leave just the 2x - 1
3. (Original post by Implo)
Show that
x²-(x-1)²=2x-1

Show me how please? Also can someone tell me what this is called so I can revise it more, thanks.

Begin by expanding the brackets:
x² - [(x-1)(x-1)] = LHS
x² - [ x² - x - x + 1 ] = LHS
x² - x² + x + x + 1 = LHS

Therefore

2x + 1 = x²-(x-1)² = RHS

This is basic multiplying out. Revise factorising quadratics
4. (x-1)² means (x-1)(x-1).
Can you multiply out two brackets?
5. (Original post by Coke Or Pepsi)
Begin by expanding the brackets:
x² - [(x-1)(x-1)] = LHS
x² - [ x² - x - x + 1 ] = LHS
x² - x² + x + x + 1 = LHS

Therefore

2x + 1 = x²-(x-1)² = RHS

This is basic multiplying out. Revise factorising quadratics
How did you get from

x² - [ x² - x - x + 1 ] = LHS

to

x² - x² + x + x + 1 = LHS ?
If multiplied out how come it isn't minus 1?
6. it is minus 1, he just made a little mistake
x²-(x-1)²=2x-1
x²-(x-1)(x-1)=2x-1
x²-(x²-2x+1)=2x-1
x²-x²+2x-1=2x-1
2x-1=2x-1
7. (Original post by Implo)
Show that
x²-(x-1)²=2x-1

Show me how please? Also can someone tell me what this is called so I can revise it more, thanks.
A "cuter" way to do it is to recognise the difference of two squares.

8. x²-(x-1)²=2x-1 --->> 80085
9. (Original post by genericusrnme)
it is minus 1, he just made a little mistake
x²-(x-1)²=2x-1
x²-(x-1)(x-1)=2x-1
x²-(x²-2x+1)=2x-1
x²-x²+2x-1=2x-1
2x-1=2x-1
She**

Yes sorry! Typo!

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