(1-x)³ + (2+x)³ = (2x+3)² - (4-x)² - 3x(x-1)
<=> 1³-3.1².x+3.1.x²-x ³+2 ³+3.2².x+3.2.x²+x³ = (2x)²+2.2x.3+3² -(4²-2.4.x+x²)-(3x²-3x)
<=> 1-3x+3x²-x³+8+12x+6x²+x³ = 4x²+12x+9-16+8x-x²-3x²+3x
<=> 1-3x+3x²-x³+8+12x+6x²+x³-4x²-12x-9+16-8x+x²+3x²-3x = 0
<=> 9x² -14x +16 =0