Вот...S(n)=(b1(q^n-1))/q-1
1)
3a-3a³=3a(1-a²)=3a(1-a)(1+a)
2)
3x²-24xy+48y²=3x²-12xy-12xy+48y²=3x(x-4y)-12y(x-4y)= =(x-y)(3x-12y)=3(x-y)(x-4y)
3)
2a³+54b²=2(a³+27)=2(a³+3³)=3(a+3)(a²-3a+9)
4)
a+5b+a²-25b²=(a+5b)+(a²-25b²)=(a+5b)+(a-5b)(a+5b)=
=(a+5b)(1+a-5b)
5)
a²-2ab+b²-25= (a-b)²-25= [(a-b)-5][(a-b)+5]=
=(a-b-5)(a-b+5)