x⁴;+y⁴;+z⁴;-2x²;y²;-2x²;z²;+2y²;z²; 分解因式
=x⁴;-2x²;y²;+y⁴;-2x²;z²;+2y²;z²;+z⁴;=(x²;-y²;)²;-2(x²;-y²;)z²;+z⁴;=(x²;-y²;-z²;)²;
證明x⁴;+y⁴;+z⁴;-2x²;y²;-2x²;z²;-2y²;z²;能被x+y+z整除
原式=(x^2+y^2)^2 -2z^2(x^2+y^2)+ z^4 -4x^2y^2 =(x^2+y^2-z^2)^2-4x^2y^2=(x^2+y^2-z^2+2xy)(x^2+y^2-z^2-2xy)=[(x+y)^2-z^2][(x-y)^2-z^2]=(x+y+z)(x+y-z)(x-y+z)(x-y-z)證明完畢
∫e^3-4x dx求不定積分
∫e^(3-4x)dx
=-1/4∫e^(3-4x)d(3-4x)
=-1/4e^(3-4x)+C