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8、若 y,z均为质数,x=yz且 x,y,z 满足 1/x+1/y=3/z,则1998x+5y+3z=
若a,b,c均为质数,x=yz且x,y,z满足1/x+1/y=3/z,则1998x+5y+3z=
人气:371 ℃ 时间:2020-05-18 01:23:00
解答
x = yz1/x+1/y=3/z1/yz + z/yz = 3y/yz ====> 3y = z+1因为y是质数,如果y是奇数的质数,z= 3y-1必为偶数,不成立所以y为偶数的质数,也就是y=2 z = 5x = 101998x+5y+3z= 19980 + 10 + 15 = 20005...
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