1..已知（x-y)^2=8,xy=2,求x^4+y^4!2.已知x+1/x=4,求(x-1/x)^2 还是第2题的题目，x^2+1/(x^2)等于多少？大哥哥大姐姐求求你们帮帮忙~

1..已知（x-y)^2=8,xy=2,求x^4+y^4!2.已知x+1/x=4,求(x-1/x)^2 还是第2题的题目，x^2+1/(x^2)等于多少？大哥哥大姐姐求求你们帮帮忙~
1..已知（x-y)^2=8,xy=2,求x^4+y^4!2.已知x+1/x=4,求(x-1/x)^2
还是第2题的题目，x^2+1/(x^2)等于多少？大哥哥大姐姐求求你们帮帮忙~

1..已知（x-y)^2=8,xy=2,求x^4+y^4!2.已知x+1/x=4,求(x-1/x)^2 还是第2题的题目，x^2+1/(x^2)等于多少？大哥哥大姐姐求求你们帮帮忙~
1.
x^4+y^4=x^4-2(xy)²+y^4+2(xy)²
=(x²-y²)²+2(xy)²
=(x-y)²(x+y)²+2(xy)²
=(x-y)²[(x-y)²+4xy]+2(xy)²
=8*[8+4*2]+2*4
=136
2.(x-1/x)²
=(x+1/x)²-4=4*4-4=12

(x+y)^2=x^2+y^2+2xy=12+4=16
x^4+y^4=(x^2+y^2)^2-2x^2y^2
=12^2-2*2*2=144-8=136
x+1/x=4,则，(x+1/x)^2=x^2+1/x^2+2=16
x^2+1/x^2=14
(x-1/x)^2=x^2-2+1/x^2=14-2=12

，136，12

1. x^4+y^4=(x^2-y^2)^2-2x^2y^2=[(x-y)^2+2xy]-2x4=[8+4]-8=4
2. (x-1/x)^2=(x+1/x)^2-4=16-4=12

x^4+y^4=(x^2+y^2)^2-2x^2·y^2=【(x-y)^2+2xy】-2·4=4
(x-1/x)^2 =(x+1/x)^2-4x·1/x=12

（x-y)^2=8, x²-2xy+y²=64 ∵xy=2 ∴x²+y²=68 x²y²=4
（x²+y²）²=68 ² x^4+y^4+2x²y²=68²
x^4+y^4=-2×4＋4624=4616
x+1/x=4 （x+1/x）²=16 x²+2+1/x²=256 x²-2+1/x²=252
（x-1/x）²=252

1.（x-y)^2
x^2-2xy+y^2=8
(x+y)^2=16
x^4+y^4=(x^2-y^2)^2+2(x^2)(y^2)=(x-y)^2(x+y)^2+2(xy)^2=120
2.(x-1/x)^2 =x^2-2+1/(x^2)=x^2+2+1/(x^2)-4=(x+1/x)^2-4=12

136;4

1. 由已知得：x*2+y*2=12 将这式两边平方得
（x*2+y*2）*2=144 可得：
x*4+2(x*2)(y*2)+y*4=x*4+y*4+8=144 可知：
x*4+y*4=136
2. 将已知两边平方得：
x^2+2+(1/x)^2=16 知 ...

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1. 由已知得：x*2+y*2=12 将这式两边平方得
（x*2+y*2）*2=144 可得：
x*4+2(x*2)(y*2)+y*4=x*4+y*4+8=144 可知：
x*4+y*4=136
2. 将已知两边平方得：
x^2+2+(1/x)^2=16 知
x^2+（1/x)^2 =14
所求的 (x-1/x)^2 = x^2-2+（1/x)^2 =14-2 =12

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1..已知（x-y)^2=8,xy=2，求x^4+y^4！！ 2.已知x+1/x=4,求(x-1/x)^2 急急急！！

1. x^4+y^4
=x^4-2x^2y^2+2x^2y^2+y^4
=(x^2-y^2)^2+2x^2y^2
=[(x+y)(x-y)]^2+2(xy)^2
=(x+y)^2(x-y)^2+2(xy)^2
=8(x+y...

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1..已知（x-y)^2=8,xy=2，求x^4+y^4！！ 2.已知x+1/x=4,求(x-1/x)^2 急急急！！

1. x^4+y^4
=x^4-2x^2y^2+2x^2y^2+y^4
=(x^2-y^2)^2+2x^2y^2
=[(x+y)(x-y)]^2+2(xy)^2
=(x+y)^2(x-y)^2+2(xy)^2
=8(x+y)^2+8
=8(x^2-2xy+2xy+2xy)+8
=8[(x-y)^2+4xy]+8
=8*(8+4*2)+8
=136
(2)
x+1/x=4,求(x-1/x)^2
(x+1/x)^2=16
x^2+2+1/x^2=16
x^2-2+2+2+1/x^2=16
(x-1/x)^2=16-4
(x-1/x)^2=12
希望你能看懂，祝你学习进步

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