№1
1) ab-ac = a(b-c)
2)mn-n = n(m-1)
3)9x-3y = 3(3x-y)
4)4,5m+1,5n = 1,5(3m+n)
5)mnk-mn = mn(k-1)
6)abc+ab = ab(c+1)
№2
1) 4(7-5x)-(12-20x) = 28-20x-12+20x = 16
2) 2(3x-y)-(5x-2y) = 6x-2y-5x+2y = x
3) 6(x+2y)-3(2x+y) = 6x+12y-6x-3y = 9y
4) 5(4x+y)-2(x-y) = 20x+5y-2x+2y = 18x +7y