2х²+4ху + 2у² = 2(х²+2ху + у²)=2(x+y)²
3а² - 6а + 3 =3(а² - 2а + 1)= 3(a+1)²
2ху² + 4 ху + 2х =2x(y²+2y+1)=2x(y+1)²
6х² -12ху + 6у² =6(х² -2ху + у²)=6(x-y)²
5m²+10m + 5 =5(m²+2m+1)=5(m+1)²
3а - 6аb + 3аb² = 3a(1-2b+b²)=3a(1-b)²
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x=arctg0+πn, nєZ
x=πn, nєZ или x=π+πn, nєZ