1 – 2ab – (a2 + b2) =? A. (1 + a - b) (1 + a + b) B. (1 + a + b)

1.	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 – 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)

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 – 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)