11, 8a3-12a2+6a-1 = ( 2a - 1 )\(^3\)
12, x3+12x2+48x+64 = ( x + 4 )\(^3\)
13, a3+b3+c3-3abc = ( a + b + c ) ( a\(^2\) + b\(^2\) +c\(^2\) - ab - bc - ca )
15, 4x4+1 = ( 2x\(^2\) + 1 ) ( 2x\(^2\) - 1 )
17, = (x\(^4\)+36x\(^2\)+324)-36x\(^2\)= (x+18)\(^2\)-36x\(^2\) = (x+18-36)(x+18+36)=(x-18)(x+54).
18, = x^5+x^4+x^3-x^4-x^3-x^2+x+1-x^2 = x^3(x+1)\(^2\)-x^2+(x+1)\(^2\)+(x+1)\(^2\) = (x\(^3\)-x\(^2\)+1)(x+1)\(^2\) (19 cmtt)