已知x=1/3k-1,y=1/6k+3,z=1/2k+3,则x^2+y^2+z^2+2xy+2xz+2yz=?
人气:455 ℃ 时间:2020-02-04 21:44:19
解答
由(x+y+z)²=1,x²+y²+z²=3,x²+y²+z²+2xy+2xz+2yz=1∴xy+xz+yz=-1∵x+y+z=1,∴x+y=1-z,①代入xy+z(x+y)=-1,xy+z(1-z)=-1∴xy=-1-z+z² ②由韦达定理:...
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