先化简再求值x²﹣1 x²﹢x÷(x²﹢1 x﹣2),其中x=根号2加1

1+(2x-4)/(x^2-a-2)]/[(x+3)/(x^2-1)]={1+2(x-2)/[(x-2)(x+1)]}(x^2-1)/(x+3)=[1+2/(x+1)](x+1)(x-1)/(x+3)

题目有误吧(x-x)x-1分之4(x-x)+(x-2)再问：(x方-x)(x-2)方再答：

是(x^2/(x-1)-x+1)/(4x^2/(1-x)-4x+1)吗原式=(x-x+1)(x+x-1)/(x-1)/((4x^2-4x+1+4x^2-x)/(1-x))=-(2x-1)/(4x^2-

[x-x/(x+1)][(x+1)/(x^2+4x+4)][(x^2-4)/(x^2-2x)]=[x^2/(x+1)][(x+1)/(x+2)^2][(x+2)(x-2)/x(x-2)]=x/(x+2

3x^3-[-x^2-2(x-x^6)]=3x^3+x^2+2(x-x^6)=3x^3+x^2+2x-2x^6x=-1原式=-3+1-2-2=-6

2x-6/x^2-4x+4÷4x-12/x^2-4÷(x+2)=2x-4x-6/x^2-12/x^2+4÷4x-4÷(x+2)=-2x-1/4x+1/x-1/(x+2)将x=1/2带入,原式得=-2*

原式=(x−1)(x+1)−x(x−2)x(x+1)×(x+1)2x(2x−1)，=2x−1x(x+1)×(x+1)2x(2x−1)=x+1x2，∵x2-x-1=0，∴x2=x+1，将x2=x+1代入

（x+2/x²-2x-x-1/x²-4x+4）÷x-4/x={(x+2)(x-2)/[x(x-2)²]-x(x-1)/[x(x-2)²]}·x/(x-4)={(

(x+2-12/x-2)/(4-x)/(x-2),其中x=-1/2=(x²-4-12)(x-2)÷(4-x)/(x-2)=(x²-16)/(4-x)=-(4-x)(4+x)/(4-

【先化简再求值】（x-1）分之x÷【(1-x分之1）-1-x】=（x-1）分之x÷（x^2/(1-x)）=-1/xx=1时,原式无意义,x=2时,原式=-1/2,x=0时,原式无意义【选择题】下列约分

(1x+2−1)÷x2+2x+1x2−4=−x−1x+2•(x+2)(x−2)(x+1)2=-x−2x+1，当x=tan60°-1=3-1时，原式=-3−1−23−1+1=-3−33=3-1．

（x-2）/（x²-1）÷（2x+2）/（x²+2x+1）+1/（x-1）,其中x=-1/2=(x-2)/(x+1)(x-1)×(x+1)²/2(x+1)=(x-2)/2

x-2/x²-1÷2x+2/x²+2x+1+1/x-1=（x+2x）+（2/x²-2/x²）+[1/x-1÷(2x)]+(1-1)=3x+0+1/(2x)+0=

=(x+1)(x-1)/x÷(x-2x+1)/x=(x+1)(x-1)/x×[-x/(x-1)==x+1当x=√2时原式=√2+1再问：对不起，是我没说明白x²-1÷(1-x分之2x-1)是

[3x/(x+2)-x/(x-2)]÷2x/(x^2-4)分子分母同时乘以x²-4=[3x(x-2)-x(x+2)]/2x=(3x²-6x-x²-2x)/2x=(2x&#

（x+1）÷[2+x分之(1+x²)]=（x+1）÷[x分之(2x+1+x²)]=(x+1)÷[x分之(x+1)²]=(x+1)·[(x+1)²分之x]=(x+

=x/(x+2)-x（x+2)/(x-5)÷（x+1）=x/(x+2)-x（x+2)/(x-5)（x+1）=[x（x-5）（x+1）-x（x+2）（x+2）]/(x+2)(x-5)(x+1)=(-8x

（x²-5-4x）-x（x²＋x-1）=x^2-5-4x-x^3-x^2+x=-x^3-3x-5当x=-1时-x^3-3x-5=-(-1)-3*(-1)-5=1+3-5=-1

(x-4)(x-2)-(x-1)(x-3)=x²-6x+8-x²+4x-3=-2x+5当x=-5/2时原式=-2*(-5/2)+5=5+5=10