Question

factorise 1-x²+2xy-y²​

Answer 1

Ans:

      1-x²+2xy-y²

 =   -(x²+y²-2xy) + (1)      (assembling)

 =   -(x-y)² + (1)²              (using identity- (a-b)² = a²+b²-2ab )

 =     (1)² - (x-y)²              

 =   (1-x+y)(1+x-y)            (using identity- a²-b² = (a+b)(a-b))

this is the answer. Whoo!!