Question

已知P=-（x-y）∧3,P=-（x-y）∧3,M=P乘Q求M的值并根据x,y的大小讨论M的符号

Answer 1

Q=[-1*(x-y)]^4

=(-4)^4*(x-y)^4

=(x-y)^4

M=PQ=-(x-y)^3*(x-y)^4=-(x-y)^7

所以x>y

x-y>0

(x-y)^7>0

M=-(x-y)^7x,

x-yy,M是负数

x