1. 3a-15b=3(a-5b)
2. 5x-2xy=x(5-2y)
3. 7mn+7mk=7m(n+k)
4. 6a²-12ab=6a(a-2b)
5. x8-x³=x³(x5-1)
6. 18ab²+9ab=9ab(2b+1)
7. 22xy²+33x²y=11xy(2y+3x)
8. -4a⁴+20a10=20a10-4a⁴=4a⁴(5a6-1)
9. 3x²+15x⁴-21x6=3x²(1+5x²-7x⁴)
10. 4a²b³-12ab²+20a²b=4ab(ab²-3b+5a)
11. 15m³-9m²n-12m²=3m²(5m-3n-4)
12. -16x²y³z-44x²y²z²+4x²yz³=4x²yz(-4y²-11yz+z²)=4x²yz(z²-4y²-11yz)