\(a.\\ 1-2y+y^2\\ =\left(y-1\right)^2\)
.\(b.\\\left(x+1\right)^2-25\\ =\left(x+1-5\right)\left(x+1+5\right)\\ =\left(x-4\right)\left(x+6\right)\)
\(c.\\ 1-4x^2\\ =\left(1-2x\right)\left(1+2x\right)\)
\(d.\\ 8-27x^3\\ =\left(2\right)^3-\left(3x\right)^3\\ =\left(2-3x\right)\left(4+6x+9x^2\right)\)
\(e.\\ 27+27x+9x^2+x^3\\ =3^3+3.3^2.x+3.3.x^2+x^3\\ =\left(x+3\right)^3\)
\(f.\\ 8x^3-12x^2y+6xy^2-y^3\\ =\left(2x\right)^3-3.\left(2x\right)^2.y+3.2x.y^2-y^3\\ =\left(2x-y\right)^3\)
\(g.\\ x^3+8y^3\\ =x^3+\left(2y\right)^3\\ =\left(x+2y\right)\left(x^2-2xy+4y^2\right)\)