1) ( x+1)(x+9) - x -1 =
( x+1)(x+9)-(x+1) =
( x+1)[(x+9)-1] =
( x+1)(x+9 -1) =
( x+1)(x+8)
2) 3x²-3 +x +1 =
3(x²-1)+(x+1)=
3(x+1)(x-1) + ( x+1)=
( x+1)[3(x-1)+1] =
( x+1)(3x - 3 +1)=
( x+1)(3x-2)
3)(2x+2)² + x+1=
( 2x+2)(2x+2) + ( x+1) =
2(x+1)*2(x+1) + ( x+1)=
4 ( x+1)² + ( x+1)=
( x+1) [4(x+1)+1]=
( x+1) ( 4x +4+1)=
( x+1)(4x+5)
4) x^4 - 1=
x^4 - 1^4=
( x²)² - ( 1²)²=
( x²-1²)(x²+1²)=
[(x+1)(x-1)](x²+1)=
( x+1)(x-1)(x+1)(x+1)=
( x+1)[(x-1)(x+1)²]=
( x-1)(x+1)^3