(1)已知|2m-5|+(2m-5n+20)²=0,求(m-n)²-(2m+n)(n-m)
问题描述:
(1)已知|2m-5|+(2m-5n+20)²=0,求(m-n)²-(2m+n)(n-m)
(2)证明(a-1)(a²(a+1)-2(a³-2a-4)-a的值与a无关
答
|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