1.57²+55²-110*57(写出运算过程,用简便方法计算)

1个回答

  • 1.

    57²+55²-110*57=57²+55²-2*55*57=(57-55)²=4

    2.

    a-b=(2010x+2008)-(2010x+2009)=-1

    b-c=(2010x+2009)-(2010x+2010)=-1

    a-c=(2010x+2008)-(2010x+2010)=-2

    a²+b²+c²-ab-bc-ca=[(a-b)²+(b-c)²+(c-a)²]/2=3

    3.

    c=5,a+b+c=12

    a²+b²=c²

    S=ab/2=6

    4.

    y(x+y)+(x+y)(x-y)-x²

    =x(x+y)-x²

    =xy