高二数学因式分解:十字乘法。下面有11练习。希望有大侠能帮我解决！想要流程！还有！

x↘ 2

x↗ 5

② x？-2x-8=(x+2)(x-4)

x↘ 2

x↗ -4

③ y？-7y+12=(y-3)(y-4)

y↘ -3

y↗ -4

④ x？+7x-18=(x-2)(x+9)

x↘ -2

x↗ 9

⑤ 2[(6x？+x)？-1](6x？+x)+5

⑥ 7x？-13x+6=(7x-6)(x-1)

7x↘ -6

x ↗ -1

⑦ -y？-4y+12=(-y+2)(y+6)

-y↘ 6

y↗ 2

⑧ 15x？+7xy-4y？=(5x+4y)(3x-y)

5x↘4y

3x↗-y

⑨ 10(x+2)？-2(x+2)+10=

⑩ x？-(a+1)x+a =(x-a)(x-1)

x↘ -a

x↗ -1

11.2x？-3xy-2y？-13x+14y-2