Объяснение:
1) –x²-2xy-1=-(x²+2xy+1)=-(x+1)²=-(x+1)(x+1)
3) 1/7 m²-2/7 m +1/7= 1/7 m²-1/7*2m+1/7=1/7(m-1)²=1/7(m-1)(m-1)
4) 18a²-12abc+2b²c²=2(9a²-6abc+b²c²)=2(3a-bc)²=2(3a-bc)(3a-bc)
