Verified answer

Ответ:

1) -2,4а * (-5b) =

= (-2,4  * (-5)) ab  =

= 12ab

2) 9a - a -8b +3b =

=(9a-a) + (-8b+3b) =

=8a -(8b-3b) =

= 8a -5b

3) a+(a-10)-(15+a) =

= a+a-10-15-a =

= (а +а -а ) + (-10  +  (-15)) =

= а -(10+15) =

= a - 25

4) -4(b-4) +7(b+2) =

= -4b +16 +7b +14 =

= (7b-4b) + (16+14)=

=3b +30 =

Пошаговое объяснение: