急~有數學唔識做？？

1.ab-ad-bc+cd
= a(b-d) + c(d-b)
= a(b-d) - c(b-d)
= (a-c)(b-d)
2.a(2次方)-ab+2a-2b
= a^2 - ab + 2a - 2b
= a(a - b) + 2(a - b)
= (a+2)(a-b)
3.16y(2次方)-25
= 16y^2 - 25
= (4y)^2 - 5^2
= (4y-5)(4y+5)
4.4x(2次方)-4xy+y(2次方)
= 4x^2 - 4xy + y^2
= (2x)^2 - 2(2x)y + y^2
= (2x - y)^2
5.4x(2次方)-4xy+y(2次方)-2x+y
= 4x^2 - 4xy + y^2 - 2x + y
= (2x)^2 - 2(2x)y + y^2 - 2x + y
= (2x - y)^2 - (2x - y)
= (2x - y)(2x - y - 1)