①(-2x-1/3y)²=____②{(-5+x)(-5-x)}²=_____③(x+y+z)(x-y-z)=___.④若x²+y²

问题描述:

①(-2x-1/3y)²=____②{(-5+x)(-5-x)}²=_____③(x+y+z)(x-y-z)=___.④若x²+y²

①(-2x-1/3y)²=4x²+4/3x+1/9y²②{(-5+x)(-5-x)}²=(25-x²)²=625-50x²+x^4③(x+y+z)(x-y-z)=x²-(y+z)²=x²-y²-z²-2yz