Question

Factorise 1-x^2-2xy-y^2

Answer 1

1-x^2-2xy-y^2
=1-(x+y)^2 (using identity (a+b)^2)

1 can be written as 1^2

(1)^2-(x+y)^2

{1-(x+y)}{1+(x+y)}

Answer 2

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' 1 - x^2 - 2 x y - y^2 '
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= 1 - ( x^2 + 2 x y + y^2 )


= 1 - ( x + y )^2

= ( 1)^2 - ( x + y )^2

= { 1 - ( x + y ) } { 1 + (x + y ) }

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= ( 1 - x - y ) ( 1 + x + y )
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