请教几道初一数学题

1.原式= 5x<2>+(9+a)x+2(a-1)
=[5x+(a-1)]*(x-2)

2.原式= 1-a<2>-b<2>-a<2>b<2>-4ab
=1-2ab-a<2>b<2>--a<2>-b<2>-2ab
= 1-ab)<2>-(a+b)<2>
=(1-ab+a+b)(1-ab-a-b)
3.原式=a<2>b-a<2>c+b<2>c-ab<2>+ac<2>-bc<2>
=b*(a<2>-c<2>)-ac*(a-c)-b<2>(a-c)
=(a-c)[b(a+c)-ac-b<2>]
=(a-c)[ab+bc-ac-b<2>]
4.原式=4x<2>+2x-y<2>-y
=(2x+y)(2x-y)+(2x-y)
=(2x-y)(2x+y+1)

25+9x+ax+2a-2=23+(2+x)a+9x

2.原式=1-a<2>-b<2>-a<2>b<2>-4ab
=1-2ab-a<2>b<2>--a<2>-b<2>-2ab
=(1-ab)<2>-(a+b)<2>
=(1-ab+a+b)(1-ab-a-b)

不会