已知,x+y+z=a,xy+yz+za=b,则x^2+y^2+z^2=
3个回答
x+y+z=a xy+yz+za=b
(x+y+z)²-2(xy+yz+za)=a²-2b
x²+y²+z²+2(xy+yz+za)-2(xy+yz+za)=a²-2b
x²+y²+z²=a²-2
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