1) b²-9-12b+3b²=4b²-12b-9
c²-12c+36-8c²-20c=-7c²-32c+36
5y²-30y+45-5y²=-30y+45
2)81a-a³=a(81-a²)=a(9-a)(9+a)
6b²-36b+54=6(b²-6b+9)=6(b-3)(b-3)
3) (x+y²)²-(y²-2)(y²+2)-2xy²=x²+2xy²+y⁴-y⁴+4-2xy²=x²+4
x=-5, 25+4=29
4)(x-2)²-36x²=(x-2-6x)(x-2+6x)=(-5x-2)(7x-2)
c²-d²-7d-7c=(c-d)(c+d)-7(d+c)=(c+d)(c-d-7)