* * * a³ -b³ =(a-b)(a²+ab+b²) , (a+b)³=a³+3a²b+3ab²+b³ * * *1) (x+1)³ -(x-1)³ =x(6x+2) ;(x+1 -(x-1))((x+1)² +(x+1)(x-1) +(x-1)²)=6x²+2x ;2(3x²+1)=6x²+2x ;x=1 .2)(x+2)³-(x-1)³=9x²+36 ;(x+2 -(x-1))((x+2)² +(x+2)(x-1) +(x-1)²)=9x²+36 ;3(3x²+3x+3) =9x²+36 ;9x²+9x+9 =9x²+36;x=3.3) (x-2)³-3x²-4=(x-3)³ ;(x-2)³ -(x-3)³ =3x²+4 ;(x-2 -(x-3))((x-2)² +(x-2)(x-3) +(x-3)²) = 3x²+4 ;3x² -15x+19 = 3x²+4 ;-15x =4-19;x=1.4) (x+3)³=x²(x+9) ;x³ +3x²*3+3x*3²+3³ =x³ +9x² ;x³ +9x²+27x +27=x³ +9x² ; 27x +27= 0 ;27x = -27 ;x= -1 .