Упростите вырожения

a + (2-a) =

9x - (8x - (1-2x)) =

4ab - (3ab - (2ab - (ab+1))) =

А + (2-а) = а+2-а=2

9 х - (8 х - (1-2 х)) = 9 х - (8 х-1+2 х) = 9 х - (10 х-1) = 9 х-10 х+1=х+1

4ab - (3ab - (2ab - (ab-1))) = 4ab - (3ab - (2ab-ab-1)) = 4ab - (3ab+ab+1) = 4ab-4ab-1=-1