1) 4m²ny²-20m = 4m(mny-5);

2) ab+6a²bmy²-3ab = ab(1+3(2amy2-1));
3) 4k²m+12k²t+m+3t = m(4k2+1)+3t(4k2+1);
4) 10pcd-15pmn+16c³d-24c²mn = 2cd(5p+8c2)-3mn(5p-8c2);