Factories:

25 – a² – b² – 2ab

Given,

25 – a² – b² – 2ab

= 25 – (a² + b² + 2ab)

By using the formula a² – b² = (a + b)(a – b)

We get,

25 – a² – b² – 2ab = 25 – (a² + b² + 2ab)

= 25 – (a + b)²

=(5)² – (a + b)²

= {5 + (a + b)}{5 – (a + b)}

= (5 + a + b)(5 – a – b)