Ответ:

1.

53³+27³/80-53×27=53³+19683/80-1431=53³+19683-114480/80=53³-94797/80

2.

а)3к³-81=3(к³-27)=3(к-3)х(к³+3к+9)

б)у²-8у+16-3ху+12х=у²-8у+28-3×у

в) m²+2mk+k²+2m+2k+1=m²+k²+1+2mk+2k+2m=(m+k+1)²

3.

a)(x+3)(x²-3x+9)-x(x-2)(x+2)=x³+27-x(x²-4)=x³+27-4³+4x=27+4x