Question

15. Выполните действия 1) (x + y)(a - b); 3) (a - b)(a +b); 2) (a - b+c)(a -c); 4) (a − 3)(a − 2)-(a - 1)(a - 4).​

Answer 1

1)(x+y)(a-b)=ax-bx+ay-by

3)(a-b)(a+b)=a²+ab-ab-b²=a²-b²

2)(a-b+c)(a-c)=a²-ac-ab+bc+ac-c²=a²-ab+bc-c²

4)(a-3)(a-2)-(a-1)(a-4)=a²-2a-3a+6-a²+4a+a-4=

=5a-5a+6-4=6-4=2