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已知x-y=-6,xy=-8.(1)求x2+y2的值;(2)求代数式(x+y+z)2+(x-y-z)(x-y+z)-2z(x+y)的值
已知x-y=-6,xy=-8.(1)求x2+y2的值;(2)求代数式(x+y+z)2+(x-y-z)(x-y+z)-2z(x+y)的值....
已知x-y=-6,xy=-8.(1)求x2+y2的值;(2)求代数式(x+y+z)2+(x-y-z)(x-y+z)-2z(x+y)的值.
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(1)∵x-y=-6,xy=-8,
∴x2+y2=(x-y)2+2xy=36-16=20;
(2)原式=(x2+y2+z2+2xy+2xz+2yz)+(x2-2xy+y2-z2)-2xz-2yz=2(x2+y2)=40.
∴x2+y2=(x-y)2+2xy=36-16=20;
(2)原式=(x2+y2+z2+2xy+2xz+2yz)+(x2-2xy+y2-z2)-2xz-2yz=2(x2+y2)=40.
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