(X+Y+Z)²=[(X+Y)+Z]²=(X+Y)²+2(X+Y)Z+Z²=X²+2XY+Y²+2XZ+2YZ+Z²=X²+Y²+Z²+2XY+2XZ+2YZ(X+Y)³=X³+3X²Y+3XY²+Y³
