oganesbagoyan

Verified answer

2.
а) a(a+3) -2(a+3) =(a+3)(a-2).
-------
б)  ax -ay +5x -5y =(ax -ay) +(5x -5y) =a(x -y) +5(x -y) =(x -y)(a +5).
* * * * * * *
4.
а) x²- xy -4x +4y =(x²- xy) -(4x-4y) =x(x-y) -4(x-y) =(x-y)(x-4).
---
или иначе x²- xy -4x +4y =(x²- 4x) -(xy-4y) =x(x-4) -y(x-4) =(x-4)(x-y).
-------
б) ab -ac -bx +cx +c-b =(ab -ac) -(bx -cx) -(b-c) =a(b -c)-x(b -c) -1*(b-c) =
(b -c)(a-x-1) .
---
или иначе ab -ac -bx +cx +c-b = (ab -bx -b) -(ac -cx -c) =  
b(a -x -1) - c(a -x -1) = (a -x -1)(b-c).