Question

factorise 1-a^2-b^2-2ab

Answer 1

Here is your answer
$1 - a {}^{2} - b {}^{2} - 2ab \\ 1 - (a {}^{2} + b {}^{2} + 2ab) \\ 1 - (a + b) { }^{2} \\ 1 - (a + b)(a + b)$
Hope it helps you

Answer 2

$\textbf {\huge {ANSWER:}}$

$1 - {a}^{2} - {b}^{2} - 2ab \\ \\ = > 1 - ( {a}^{2} + {b}^{2} + 2ab) \\ \\ identity - \\ {a}^{2} + {b}^{2} + 2ab = {(a + b)}^{2} \\ \\ = > {1}^{2} - {(a + b)}^{2} \\ \\ identity - \\ {a}^{2} - {b}^{2} = (a - b)(a + b) \\ \\ = > (1 - a + b)(1 + a + b)$