Question

how was -2ab changed to 2ab..?

please refer above attachment...​

Answer 1

Answer:

here is your answer dude

Step-by-step explanation:

=1-2ab-(a²+b²)

=1-2ab-a²-b² taking (-) as common here

1-( a²+b²+2ab)

As we have to get it in form (a+b)²