老师留的提高题!(1) M ,N 均为正数且 M不等于N 比较2分之M+2 与 M+N分之2MN (2)若X+Y+Z=30,3X+Y+-Z=50 X,Y,Z均为非负数,求5X+4Y+2Z的取值范围
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![老师留的提高题!(1) M ,N 均为正数且 M不等于N 比较2分之M+2 与 M+N分之2MN (2)若X+Y+Z=30,3X+Y+-Z=50 X,Y,Z均为非负数,求5X+4Y+2Z的取值范围](/uploads/image/z/1157962-58-2.jpg?t=%E8%80%81%E5%B8%88%E7%95%99%E7%9A%84%E6%8F%90%E9%AB%98%E9%A2%98%21%EF%BC%881%EF%BC%89+M+%2CN+%E5%9D%87%E4%B8%BA%E6%AD%A3%E6%95%B0%E4%B8%94+M%E4%B8%8D%E7%AD%89%E4%BA%8EN+%E6%AF%94%E8%BE%832%E5%88%86%E4%B9%8BM%2B2+%E4%B8%8E+M%2BN%E5%88%86%E4%B9%8B2MN+%EF%BC%882%EF%BC%89%E8%8B%A5X%2BY%2BZ%3D30%2C3X%2BY%2B-Z%3D50+X%2CY%2CZ%E5%9D%87%E4%B8%BA%E9%9D%9E%E8%B4%9F%E6%95%B0%2C%E6%B1%825X%2B4Y%2B2Z%E7%9A%84%E5%8F%96%E5%80%BC%E8%8C%83%E5%9B%B4)
老师留的提高题!(1) M ,N 均为正数且 M不等于N 比较2分之M+2 与 M+N分之2MN (2)若X+Y+Z=30,3X+Y+-Z=50 X,Y,Z均为非负数,求5X+4Y+2Z的取值范围
老师留的提高题!
(1) M ,N 均为正数且 M不等于N 比较2分之M+2 与 M+N分之2MN
(2)若X+Y+Z=30,3X+Y+-Z=50 X,Y,Z均为非负数,求5X+4Y+2Z的取值范围
老师留的提高题!(1) M ,N 均为正数且 M不等于N 比较2分之M+2 与 M+N分之2MN (2)若X+Y+Z=30,3X+Y+-Z=50 X,Y,Z均为非负数,求5X+4Y+2Z的取值范围
(1)2分之M+2大于M+N分之2MN
(2) x+y+z=30①
3x+y-z=50②
①+②,得
4x+2y=80
Y=40-2x
②-①,得
2x-2z=20
Z=x-10
∵y≥0
z≥0
∴10≤x≤20
5x+4y+2z
=3( X+Y+Z)+(3X+Y-Z)-X
=90+50-X
=140-x
∴120≤5x+4y+2z≤130