知识大全已知x^2+3x-1=0,则代数式1/x-2·x^2-4x+4/x+1-x-1/x+2的值为

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已知x^2+3x-1=0,则代数式1/x-2·x^2-4x+4/x+1-x-1/x+2的值为

解：
因为x²+3x-1=0
所以x²+3x=1
1/（x-2）×（x²-4x+4）/（x+1）-（x-1）/（x+2）
=1/（x-2）×（x-2）²/（x+1）-（x-1）/（x+2）
=（x-2）/（x+1）-（x-1）/（x+2）
=（x-2）（x+2）/（x+1）（x+2）-（x-1）（x+1）/（x+1）（x+2）
=（x²-4-x²+1）/（x²+3x+2）
=-3/（x²+3x+2）
=-3/（1+2）
=-3/3
=-1

已知x平方+3x-8=0,求代数式1/x-2*x^2-4x+4/x+1-x-1/x+2的值

x^2+3x-8=0
x^2+3x=8
1/(x-2) * (x^2-4x+4)/(x+1) - (x-1)/(x+2)
= 1/(x-2) * (x-2)^2/(x+1) - (x-1)/(x+2)
= (x-2)/(x+1) - (x-1)/(x+2)
= (x-2)(x+2)-(x-1)(x+1) / (x+2)(x+1)
= (x^2-4-x^2+1) / (x^2+3x+2)
= -3 / (8+2)
=-3/10

已知：x^3+3x-8=0,求代数式1/x-2乘以x^2-4x+4/x+1 -x-1/x+2

x^2+3x-8=0
x^2+3x=8
1/(x-2) * (x^2-4x+4)/(x+1) -(x-1)/(x+2)
= 1/(x-2) * (x-2)^2/(x+1) -(x-1)/(x+2)
= (x-2)/(x+1) - (x-1)/(x+2)
= [ (x-2)(x+2) - (x-1)(x+1) ] / [ (x+1)(x+2)]
= [ x^2-4-x^2+1] / [ (x+1)(x+2)]
= -3 / (x^2+3x+2)
= -3 / (8+2)
= -3/10

已知x²+3x-1=0，求代数式1/x-2 * x²-4x+4/x+1 - x-1/x+2的值

解析，
由于，x²+3x-1=0，
那么，x²+3x=1。
1/(x-2)*(x²-4x+4)/(x+1)-(x-1)/(x+2)
=(x-2)/(x+1)-(x-1)/(x+2)
=-3/[(x+1)(x+2)]
=-3/(x²+3x+2)
=-3/(1+2)
=-1

已知2x²-x-2=0,则代数式x²+1/x²=,代数式x∧4+1/x∧4=

∵2x-x-2=0 ∴x=(x+2)／2 ∴x+ 1/x=(x+2)/2 + 2 /(x+2) =[(x+2)+2×2]/[2(x+2)] =（x+4x+8）/[2(x+2)] =[(x+2)／2 +4x+8]/[2(x+2)] =[(x+2) +8x+16]/[4(x+2)] =(9x+18)/[4(x+2)] =[9(x+2)]/[4(x+2)] =9/4 =2又1/4 ∴x的四次方+x的四次方分之1=(x+ 1/x)－2 =(9/4)－2 =81/16 －2 =49/16 =3又1/16

已知x^2-5x-2=0,则代数式(x-2)^3-(x-1)^2+1/x-2的值为

解：
原所求代数式为：
[(x-2)³-(x-1)²+1]/(x-2)
=(x-2)²-[(x-1)²-1]/(x-2)
=(x-2)²-[(x-1+1)(x-1-1)]/(x-2)
=(x-2)²-x
=x²-4x+4-x
=x²-5x+4
由x²-5x-2=0可得：
x²-5x=2
因此：
[(x-2)³-(x-1)²+1]/(x-2)
=(x-2)²-[(x-1)²-1]/(x-2)
=(x-2)²-[(x-1+1)(x-1-1)]/(x-2)
=(x-2)²-x
=x²-4x+4-x
=x²-5x+4
=6

已知代数式12x-(x-2)/3+1的值为零,求代数式(3x-1)/4+(2x+1)/3的值

12x-(x-2)/3+1=0,则x=-1/7
把x=-1/7带入代数式(3x-1)/4+(2x+1)/3中，计算结果为-120/7
希望你满意

已知1/x-1/2y=1/3，则代数式（2x+3xy-4y）/（x-3xy-2y）的值为

解：
(2x+3xy-4y)/(x-3xy-2y)
=(2/y+3-4/x)/(1/y-3-2/x) （分子分母除以xy）
=(-4/x+2/y+3)/(-2/x+1/y-3)
=[-4(1/x-1/2y)+3]/[-2(1/x-1/2y)-3 ]
=(-4*1/3+3)/(-2*1/3-3)
=(-4/3+3)/(-2/3-3)
=5/3 /(-11/3)
=-5/11

已知x^2-5x-1991=0,则代数式(x-2)^4+(x-1)^2-1/(x-1)(x-2)的值

x^2-5x-1991=0
解答
x1= 47.1906
x2=-42.1906
代入
y =
1.0e+006 *
4.1727
3.8153

已知X^2-5X-1991=0,则代数式[(X-2)^4+(X-1)^2-1]/(x-2)(的值

∵X^2-5X-1991=0
∴(x-2)²=x+1995,x²=5x+1991,x=﹙5±√7989﹚/2
∴[(X-2)^4+(X-1)^2-1]/(x-2)
＝[(X-2)^4+x(x-2)]/(x-2)
=(x-2)^3+x
=(x+1995)x+x
=x²+1996x
=5x+1991+1996x
=2001x+1991=2001×﹙5±√7989﹚/2+1991=13987/2±2001/2√7989

知识大全 已知x^2+3x-1=0,则代数式1/x-2·x^2-4x+4/x+1-x-1/x+2的值为