1)6x²y²-6x⁴ =6x²(y² - x²)=6x²(y-x)(y+x)
2)-9m²+9n²=-9(m²-n²)=-9(m-n)(m+n)
3)25c²-1=(5c-1)(5c+1)
4)242c⁴-2k⁴=2(121c⁴-k⁴) = 2(11c²-k²)(11c²+k²)
5)192a³y²-3a=3a(64a²y² - 1)=3a(8ay-1)(8ay+1)
6)9k¹²-30k⁶t⁵+25t¹⁰=9(k⁶)² - 30k⁶t⁵ + 25(t⁵)² = (3k⁶ - 5t⁵)²
7)3m⁶y+18m³y⁵+27y¹⁰=3((m³)² + 6m³y⁵ + 9(y⁵)²)=3(m³ + 3y⁵)