【1】9×10^2010-10^2011

1个回答

  • 【1】9×10^2010-10^2011

    =9×10^2010-10×10^2010

    =-10^2010

    【2】9³-9²-8×9²

    =9²(9-1-8)

    =0

    【3】(2x+3)²-2(2x+3)(3x-2)+(3x-2)²

    =(2x+3+3x-2)²

    =(5x+1)²

    【4】2(x-1)(x²+x+1)+6(x+1)²=32+2(x+1)(x²+2x+1)

    2x³-2+6(x+1)²=32+2(x³+1)+2(x+1)×3x

    6x²+12x+6=32+4+6x²+6x

    6x=30

    x=5

    【5】求证:对于任意整数n,(2n+1)²-1一定能被8整除.

    (2n+1)²-1

    =(2n+1+1)(2n+1-1)

    =4n(n+1)

    ∵n(n+1)能被2整除

    ∴4n(n+1)能被8整除

    (2n+1)²-1一定能被8整除

    【6】设n为整数,求证(2n+1)²-25能被4整除

    (2n+1)²-25

    =(2n+1+5)(2n+1-5)

    =4(n+3)(n-2)

    ∴(2n+1)²-25

    【7】如果2x-y=10,求代数式[(x²+y²)-(x-y)²+2y(x-y)]÷4y的值

    [(x²+y²)-(x-y)²+2y(x-y)]÷4y

    =(x²+y²-x²+2xy-y²+2xy-2y²)÷4y

    =(4xy-2y²)÷4y

    =(2x-y)/2

    =10/2

    =5

    【8】已知x(x-1)-(x²-y)=2,求(x²+y²)÷2-xy的值

    x(x-1)-(x²-y)=2

    x²-x-x²+y=2

    -x+y=2

    x-y=-2

    (x²+y²)÷2-xy

    =(x²-2xy+y²)/2

    =(x-y)²/2

    =4/2

    =2

    【9】已知a-b-c=4,求1/2a(a-b-c)+b(1/2×c-1/2×a+1/2×b)+1/2×c(b+c-a)的值

    1/2表示二分之一

    1/2a(a-b-c)+b(1/2×c-1/2×a+1/2×b)+1/2×c(b+c-a)

    =1/2a(a-b-c)-1/2b(a-b-c)-1/2c(a-b-c)

    =1/2(a-b-c)²

    =1/2×16

    =8

    【10】已知a=1/2×m+1,b=1/2×m+2,c=1/2×m+3,求a²-ab+b²-ac-bc+c²的值

    a²-ab+b²-ac-bc+c²

    =1/2[(a-b)²+(b-c)²+(c-a)²]

    =1/2[(-1)²+(-1)²+2²]

    =3