Question

1 – 2ab – (a² + b²) =? 

A. (1 + a - b) (1 + a + b) 

B. (1 + a + b) (1 - a + b) 

C. (1 + a + b) (1 - a - b) 

D. (1 + a - b) (1 - a + b)

Answer 1

1 – 2ab – (a² + b²) = 1 – 2ab – a² – b² 

= 1 – (2ab + a² + b²) 

= 1 – (a + b)² 

= (1 – a – b)(1 + a + b) \(\because\) a² – b² = (a – b)(a + b)