已知|2m-5|+(2m-5n+20)的2次方=0,求(-2m的2次方)-2m(5n-2m)+3n(6m-5n)-3n(
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已知|2m-5|+(2m-5n+20)的2次方=0,求(-2m的2次方)-2m(5n-2m)+3n(6m-5n)-3n(4m-5n)的值.
已知,|2m-5|+(2m-5n+20)^2 = 0 ,且绝对值和平方值都大于等于0,
可得:2m-5 = 0 ,2m-5n+20 = 0 ,
解得:m = 5/2 ,n = 5 .
(-2m)^2-2m(5n-2m)+3n(6m-5n)-3n(4m-5n)
= 4m^2-10mn+4m^2+18mn-15n^2-12mn+15n^2
= 8m^2-4mn
= 4m(2m-n)
= 0
可得:2m-5 = 0 ,2m-5n+20 = 0 ,
解得:m = 5/2 ,n = 5 .
(-2m)^2-2m(5n-2m)+3n(6m-5n)-3n(4m-5n)
= 4m^2-10mn+4m^2+18mn-15n^2-12mn+15n^2
= 8m^2-4mn
= 4m(2m-n)
= 0
已知|2m-5|+(2m-5n+20)的2次方=0,求(-2m的2次方)-2m(5n-2m)+3n(6m-5n)-3n(
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