已知正整数a,b满足4a+b=30,则使得1/a+1/b取最小值是,实数对(a,b)是

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已知正整数a,b满足4a+b=30,则使得1/a+1/b取最小值是,实数对(a,b)是已知正整数a,b满足4a+b=30,则使得1/a+1/b取最小值是,实数对(a,b)是已知正整数a,b满足4a+b

已知正整数a,b满足4a+b=30,则使得1/a+1/b取最小值是,实数对(a,b)是
已知正整数a,b满足4a+b=30,则使得1/a+1/b取最小值是,实数对(a,b)是

已知正整数a,b满足4a+b=30,则使得1/a+1/b取最小值是,实数对(a,b)是
(4a+b)*(1/a+1/b)=5+4a/b+b/a>=5+2*2=9
当且仅当4a/b=b/a,即b=2a,a=5,b=10时等号成立
得3/10
4a+b=30………………(1)
1/a+1/b=3/10…………(2)
a=5,
b=10