已知|x-2|+|y-4|=0 求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值已知|x-2|+|y-4|=0求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值求的内容给大家读一下xy分之一+(x+2)(y+2)分之一+(x+4)(y+4)分
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已知|x-2|+|y-4|=0 求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值已知|x-2|+|y-4|=0求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值求的内容给大家读一下xy分之一+(x+2)(y+2)分之一+(x+4)(y+4)分
已知|x-2|+|y-4|=0 求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值
已知|x-2|+|y-4|=0
求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值
求的内容给大家读一下xy分之一+(x+2)(y+2)分之一+(x+4)(y+4)分之一+等等+(x+1994)(y+1994)分之一
我光知道x=2 y=4,求的那步不会做
为什么要把1/2单独提出来？不懂
已知|x-2|+|y-4|=0 求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值已知|x-2|+|y-4|=0求/1xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)的值求的内容给大家读一下xy分之一+(x+2)(y+2)分之一+(x+4)(y+4)分
1.
绝对值项恒非负,两绝对值项之和=0,两绝对值项分别=0
x-2=0 x=2
y-4=0 y=4
y=x+2
1/(xy)+1/[(x+2)(y+2)]+1/[(x+4)(y+4)]+...+1/[(x+1994)(y+1994)]
=1/[x(x+2)]+1/[(x+2)(x+4)]+1/[(x+4)(x+6)]+...+1/[(x+1994)(x+1996)]
=(1/2)[1/x-1/(x+2)+1/(x+2)-1/(x+4)+1/(x+4)-1/(x+6)+...+1/(x+1994)-1/(x+1996)]
=(1/2)[1/x -1/(x+1996)]
=(1/2)(1/2 -1/1998)
=499/1998
|x-2|+|y-4|=0
|x-2|≥0
ly-4l≥0
所以 |x-2|=0 x=2
ly-4l=0 y=4
1/xy + 1/(x+2)(y+2) + 1/(x+4)(y+4) +…+ 1/(x+1994)(y+1994)
=1/2x4+1/4x6+1/6x8+...+1/1996x1998
=1/2(1/2-1/4)+1/2(1/4-1/6)+1/2(1/6-1/8)+...+1/2(1/1996-1/1998)
=1/2(1/2-1/1998)
=1/2x998/1998
=499/1998
|x-2|+|y-4|=0
x=2 y=4
y=2x
1/xy=1/（x*2x）=1/2x^2
1/(x+2)(y+2)=1/【x+x)(2x+x)=1/6x^2 =1/2*3 分母加2 系数为2的3倍
1/(x+4)(y+4=1/[x+2x)(2x+2x)=1/12x^2=1/2*6x^2 分母加4 系数为2的4倍
提出1/x^2