1)(5a-7)(3a+1)=5a.3a+5a.1-7.3a-7.1=15a²+5a-21a-7=
=15a²-16a-7
(3b+7)(4-3b)=12b-9b²+28-21b=-9b²-9b+28
2)7aˇ4+11aˇ7=aˇ4(7+11aˇ3)
3mˇ3nˇ5+21mˇ5nˇ3-33mˇ2nˇ4=3mˇ2nˇ3(mn2+7mˇ3-11n)
5x-10xy=5x(1-2y)
3mˇ3-12mˇ4=3mˇ3(1-4m)
3)7ax+7bx=7x(a+b)
3c+15d=3(c+5d)
3x+6xˇ2=3x(1+2x)
4)5a(b+c)-10(b+c)=5(b+c)(a-2)
2a-ac+2b-cb=a(2-c)+b(2-c)=(2-c)(+ab)
3a(b-4)-2b+8=3a(b-4)-2(b-4)=(b-4)(3a-2)
xˇ3+3xˇ2-x-3=xˇ2(x+3)-(x+3)=(x+3)(xˇ2-1)=(x+3)(x+1)(x-1)
9x+ay+9y+ax=9x+ax+9y+ay=x(9+a)+y(9+a)=(9+a)(x+y)
ax+ay-x-y=a(x+y)-(x+y)=(x+y)(a-1)
7a-7b+an-bn=7(a-b)+n(a-b)=(a-b)(7+n)