Ответ:

1) 9x+xy+8y+72= x*(9+y)+8*(y+9)= (9+y)*(x+8)

2)bx-4b+ax-4a= b*(x-4)+a*(x-4)= (x-4)*(b+a)

3)4a-ay-by+4b= a*(4-y)+b*(-y+4)= (4-y)*(a+b)

4)7ax-ay+7bx-by= a*(7x-y)+b*(7x-y)= (7x-y)*(a+b)

5)11ay-by-77a+7b= y*(11a-b)-7*(11a-b)= (11a-b)*(y-7)

6) 13x-ax+13y-ay= x*(13-a)+y*(13-a) = (13-a)*(x+y)

Объяснение: