1988(x-y)+1989(y-z)+1990(z-x)=0,1998^2(x-y)+1989^2(y-z)+1990^2(z-x)=1989,求z-y的值

x-y/(z-x)(z-y) 一y-z/(x-y)(x-z) ＋z-x/(y-z)(y-x) x^-(y-z)^/(x+y)^-z^ 计算（x+y-z)(x-y-z) 计算：(x-y+z)(-x+y+z) (x+y-z)(x-y+z)= 1988(x-y)+1989(y-z)+1990(z-x)=0,1998^2(x-y)+1989^2(y-z)+1990^2(z-x)=1989,求z-y的值 x y y ...y z x y ...y z z x ...y ........z z z ...x 求解行列式. 1998(x-y)+1989(y-z)+1990(z-x)=0,1998^2(x-y)+1989^2(y-z)+1990^2(z-x)=1989,求z-y x/y>0,y/z z/(x-y) × y/(x+y) x+y>z 0 用乘法公式计算(x+y)(x-y)+(-y-z)(-y+z)+(-x+z)(z+x) 计算：（X+y+z)(-x+y+z)(x-y+z)(x+y-z) （x+y-z）（x-y+z）-（x+y+z）（x-y-z） 因式分解 ：（x+y-z)(x-y-z)+(y-x+z)(y-x-z) 因式分解测试题x(x+y-z)+y(x+y-z)+z(z-x-y) (x+y+z)(-x+y+z)(x-y+z)(x+y-z)等于什么? (x-y+z)²