3. 1) 3mn²-12m-5n²+20=3m(n²-4)-5(n²-4)=(3m-5)(n²-4)=(3m-5)(n-2)(n+2)
2) 9-4x²-48xy-144y²=9-4·(x²+2·6y+36y²)=9-4(x+6y)²=3²-[2·(x+6y)]²=
=[3-2·(x+6y)]·[3+2·(x+6y)]=[3-2x-12y]·[3+2x+6y]
3) xy³-y³-8x+8=y³(x-1)-8(x-1)=(x-1)(y³-8)=(x-1)(y³-2³)=(x-1)(y-2)(y²+xy+y²)
4) 243x⁵-32=3⁵x⁵-2⁵=(3x)⁵-2⁵=(3x-2)((3x)⁴+(3x)³2+(3x)²2²+(3x)2³+2⁴)=
= (3x-2)(81x⁴+54x³+36x²+24x+16)