1
а) (2-3n)²-9n⁴ =(2-3n-3n²)(2-3n+3n²)
в) x⁶-x⁴-x²+1=x^4(x²-1)-(x²-1)=(x²-1)(x^4-1)=(x²-1)(x²-1)(x²+1)=
=(x-1)²(x+1)²(x²+1)
б) (а-5)²+2(5-а)+1=(5-a)²+2(5-a)+1=[(5-a)+1]²=(6-a)²
г) 8b³- 1/27=(2b-1/3)(4b²+2b/3+1/9)
2
(87²-13²)/(91²-2*17*91+17²)=(87-13)(87+13)/((91-17)²=
=74*100/74²=100/74=50/37=1 13/37
3
(х-3)²+ (3-х)(х+3)=(х+2)²-х²
x²-6x+9+9-x²=x²+4x+4-x²
4x+6x=18-4
10x=14
x=1,4
4
х²-7х+12=x(x-3)-4(x-3)=(x-3)(x-4)
5
(30³+19³)/(30²-570+19²)=(30+19)(30²-30*19+19²)/(30²-570+19²)=49