1999^2-1998^2=-x^2+4xy-4y^2=4(a-b)^2-9a+9b=1/2x^2+2xy+2y^2=

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1999^2-1998^2=-x^2+4xy-4y^2=4(a-b)^2-9a+9b=1/2x^2+2xy+2y^2=1999^2-1998^2=-x^2+4xy-4y^2=4(a-b)^2-9a+9

1999^2-1998^2=-x^2+4xy-4y^2=4(a-b)^2-9a+9b=1/2x^2+2xy+2y^2=
1999^2-1998^2=
-x^2+4xy-4y^2=
4(a-b)^2-9a+9b=
1/2x^2+2xy+2y^2=

1999^2-1998^2=-x^2+4xy-4y^2=4(a-b)^2-9a+9b=1/2x^2+2xy+2y^2=
1999^2-1998^2=(1999+1998)(1999-1998)=3997
-x^2+4xy-4y^2= -(x^2-4xy+4y^2)=-(x-2y)^2
4(a-b)^2-9a+9b=4(a-b)^2-9(a-b)=(a-b)(4a-4b-9)
1/2x^2+2xy+2y^2=1/2(x^2+4xy+4y^2)=1/2(x+2y)^2

已知X=-0.239,求 |X-1|+|X-3|+|X-5|+.+|X-1999|-|X|-|X-2|-|X-4|-.-|X-1998|的值谁帮我做一下一个“整式的乘法”的问题请先阅读下列解题过程,再仿做下面的问题.已知X*X + X - 1=0,求X*X*X + 2*X*X + 3的值.解X*X*X + 2X*X +3=X*X*X +X*X -X +X*X +X +3=X{X*X +X -1} +X*X +X -1 +4=0+0+4=4+ x + X*X + X*X*X=0.+ X*X + X*X*X x+2x+3x+4x+5x+6x+7x+8x+9x=9x-8x-7x-6x-5x-4x-3x-2x-x.x等于多少? (x/x-2)+(2/x*2+2x)-(x+6/x*2-4)化简,=x^2/x(x-2)+(2x-4)/x(x^2-4)-(x^2+6x)/x(x^2-4)=x^2/x(x-2)-(x+2)/x(x-2)=(x-2)(x+1)/x(x-2)=(x+1)/x 先化简,再求值：（x-2/x-x+2/x)/x-2/4x,x=2011 (x-3/x-2)-(x-2/x-1)=(x-5/x4) -(x-4/x-3) x-2x+3x-4x+5x.+99x-100x=25求解 2x+3x+4x+5x+x+6x+7x=100 x(x+1)+(x+2)+(x+3)+(x+4)+(x+5) = 27求x *-----------------------------------------------*| 6 4 X | 8 X X | X X 5 || X X X | X X X | X 7 8 || X X X | X X X | X X X ||---------------+---------------+--------------- || X X X | X X X | 5 1 X || X X X | X 6 X | X X X || 8 X X | 3 5 X | 2 X X || 已知x^2+x+1=0,求x^2000+x^1999+x^1998+…+x+1的值已知x^3+x^2+x+1=0 求x^1999+x^1998+x^1997的值证明方程x^2000+x^1999+x^1998+x^1007+.x^2+x=0至少有两个实根解方程(x/x(x+2))+(x/(x+2)(x+4))+.+x/(x+8)(x+10)=1 若x^2-5x-1999=0,求[(x-2)^4+(x-1)^2-2]/[(x-1)(x-2)]若x^2-5x-1999=0,求[(x-2)^4+(x-1)^2-1]/[(x-1)(x-2)] X+X+X+(X-1)+(X-2)+(X-3)+(X-4)=10(X-3)+(X-4) x+2/x+1-x+4/x+3=x+6/x+5-x+8/x+7 x=? x-x/4-120=x/2