已知x,y,z是正整数,且满足x^3-y^3-z^3=3xyz,x^2=2(y+z),求xy+yz+zx的值
人气:206 ℃ 时间:2019-10-23 09:07:22
解答
这个只能解不定方程了因为x,y,z是正整数所以,x^3-y^3-z^3=3xyz>0故有,x^3>y^3;且x^3>z^3即,x>y且x>z同理有,x^2=2(y+z)<2(x+x)=4x所以,正整数 x<4且由x^2=2(y+z)可知x是偶数所以,只有x=2又因为x>y且x>z且均...
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