`a, 1 - 8x^3 = (1-2x)(1+2x + 4x^2)`
`b, x^3 + 3x^2 + 3x + 1 = (x+1)^3`
`c, (x+y)^2 - 9x^2 = (x+y+3x)(x+y-3x)`
`= (4x+y)(y-2x)`
`d, 10x - 25 - x^2 = -(x-5)^2`
`e, (2x-1/2)(4x^2 +x + 1/4)`.`
`f, 1/25 x^2 - 64x^2 = (1/5x - 8x)(1/5x+8x)`
`= (-39/5x)(41/5x)`
`g, -x^3 + 9x^2 - 27x + 27 = -(x-3)^3`