1.(x-2y)(2y-x)=2.(a-b)^2=_____=(a+b)^23.x-1/X=5,则x^2+1/x^2=____4.若a(a-1)-(a^2-b)=4,则(a^2+b^2)/2-ab的值是——5.已知x-y=7,xy=60,求x^2+y^2及(x+y)^2的值最主要第五题

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1.(x-2y)(2y-x)=2.(a-b)^2=_____=(a+b)^23.x-1/X=5,则x^2+1/x^2=____4.若a(a-1)-(a^2-b)=4,则(a^2+b^2)/2-ab的值是——5.已知x-y=7,xy=60,求x^2+y^2及(x+y)^2的值最主要第五题
1.(x-2y)(2y-x)=
2.(a-b)^2=_____=(a+b)^2
3.x-1/X=5,则x^2+1/x^2=____
4.若a(a-1)-(a^2-b)=4,则(a^2+b^2)/2-ab的值是——
5.已知x-y=7,xy=60,求x^2+y^2及(x+y)^2的值
最主要第五题

1.(x-2y)(2y-x)=2.(a-b)^2=_____=(a+b)^23.x-1/X=5,则x^2+1/x^2=____4.若a(a-1)-(a^2-b)=4,则(a^2+b^2)/2-ab的值是——5.已知x-y=7,xy=60,求x^2+y^2及(x+y)^2的值最主要第五题
⒈原式=(x-2y)[-(x-2y)]=-(x-2y)²=-x²+4xy-4y²
⒉(a-b)²=(a-b)²+4ab=(a+b)²
⒊两边平方:(x-1/x)²=x²-2×x×(1/x)+1/x²=x²+1/x²-2=25
则x²+1/x²=27
⒋a(a-1)-(a²-b)=a²-a-a²+b=b-a=4
两边平方:(b-a)²=b²+a²-2ab=16
∴a²+b²=16+2ab
∴原式=(16+2ab)/2-ab=8+ab-ab=8
⒌x²+y²=x²-2xy+y²+2xy=(x-y)²+2xy=7²+2×60=49+120=169
(x+y)²=x²-2xy+y²+4xy=(x-y)²+4xy=7²+4×60=49+240=289

(5) x²+y²=(x-y)²+2xy=7²+2×60=169 (x+y)²=(x-y)²+4xy=7²+4×60=289

  1. (x-2y)(2y-x)=-x^2+4xy-4y^2
    2.(a-b)^2=_a^2-2ab+b^2   (a+b)^2=a^2+2ab+b^2
    3.x-1/X=5,则x^2+1/x^2=__27__           &nbs...

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    1. (x-2y)(2y-x)=-x^2+4xy-4y^2
      2.(a-b)^2=_a^2-2ab+b^2   (a+b)^2=a^2+2ab+b^2
      3.x-1/X=5,则x^2+1/x^2=__27__                                       ! (x-1/x)^2=x^2+(1/x)^2-2=25
      4.若a(a-1)-(a^2-b)=4,则(a^2+b^2)/2-ab的值是——
      5.已知x-y=7,xy=60,求x^2+y^2及(x+y)^2的值

    2.  x²+y²=(x-y)²+2xy=7²+2×60=169        (x+y)²=(x-y)²+4xy=7²+4×60=289

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