Question

（1）已知|2m-5|+(2m-5n+20)²=0,求(m-n)²-(2m+n)(n-m)

Answer 1

|2m-5|+(2m-5n+20)²=0

∴2m-5=0

2m-5n+20=0

∴m=5/2

n=5

(m-n)²-(2m+n)(n-m)

=(m-n)²+(2m+n)(m-n)

=(m-n)(m-n+2m+n)

=3m(m-n)

=3×5/2×(5/2-5)

=-75/4

第二个题目不完整