x = yz
1/x+1/y=3/z
1/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 = 5 x = 10
1998x+5y+3z= 19980 + 10 + 15 = 20005
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=
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