Question

①（z减y）（y减x）（x减z）分之（x减y）（y减z）（z减x)②x平方减y平方分之y减x这些怎么化简

Answer 1

(x-y)(y-z)(z-x)/((z-y)(y-x)(x-z))=(x-y)(y-z)(z-x)/(-(y-z)(x-y)(z-x))=-1

(y-x)/(x²-y²)=-(x-y)/(x+y)(x-y)=-1/(x+y)

(m+2n)/(m²-4n²)=(m+2n)/((m+2n)(m-2n))=)1/(m-2n)

把m=1,n=3代入得：1/(1-2*3)=-1/5