初二数学题!高手来!在线=哦!1.已知a+b+c=0,则a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)的值等于多少? 2 2 12.已知2x -3x-2=0,求x + ——的值. 2 x（是2x平方-3x-2=

初二数学题!高手来!在线=哦!1.已知a+b+c=0,则a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)的值等于多少? 2 2 12.已知2x -3x-2=0,求x + ——的值. 2 x（是2x平方-3x-2=
初二数学题!高手来!在线=哦!
1.已知a+b+c=0,则a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)的值等于多少?
2 2 1
2.已知2x -3x-2=0,求x + ——的值.
2
x
（是2x平方-3x-2=0,求x的平方+x的平方分之1的值）
3.若ab=1,则（1+a的平方分之1 + 1+b的平方分之1的值为多少,请自己那笔写,这上面不好打出来,谢谢大家帮忙!

初二数学题!高手来!在线=哦!1.已知a+b+c=0,则a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)的值等于多少? 2 2 12.已知2x -3x-2=0,求x + ——的值. 2 x（是2x平方-3x-2=
(1)a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a/b+a/c+b/c+b/a+c/a+c/b
=(a+c)/b+(a+b)/c+(b+c)/a
a+b+c=0
(a+c)/b+(a+b)/c+(b+c)/a
=-b/b-c/c-a/a
=-3
(2)2x^2-3x-2=0
(2x+1)(x-2)=0
x1=-0.5,x2=2
x1=-0.5,x^2+1/x^2=4.25
x1=2,x^2+1/x^2=4.25
(3)1/(1+a^2)+1/(1+b^2)
=(1+b^2)/ (1+a^2)(1+b^2)+(1+a^2)/(1+a^2)(1+b^2)
=(2+a^2+b^2)/[a^2+b^2+(ab)^2+1]
=(2+a^2+b^2)/(a^2+b^2+2)
=1

(1)a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a/b+a/c+b/c+b/a+c/a+c/b
=(a+c)/b+(a+b)/c+(b+c)/a
a+b+c=0
(a+c)/b+(a+b)/c+(b+c)/a
=-b/b-c/c-a/a
=-3
(2)2x^2-3x-2=0
(2x+1)(x-...

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(1)a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a/b+a/c+b/c+b/a+c/a+c/b
=(a+c)/b+(a+b)/c+(b+c)/a
a+b+c=0
(a+c)/b+(a+b)/c+(b+c)/a
=-b/b-c/c-a/a
=-3
(2)2x^2-3x-2=0
(2x+1)(x-2)=0
x1=-0.5,x2=2
x1=-0.5,x^2+1/x^2=4.25
x1=2,x^2+1/x^2=4.25
(3)1/(1+a^2)+1/(1+b^2)
=(1+b^2)/ (1+a^2)(1+b^2)+(1+a^2)/(1+a^2)(1+b^2)
=(2+a^2+b^2)/[a^2+b^2+(ab)^2+1]
=(2+a^2+b^2)/(a^2+b^2+2)
=1

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(1)a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a/b+a/c+b/c+b/a+c/a+c/b
=(a+c)/b+(a+b)/c+(b+c)/a
a+b+c=0
(a+c)/b+(a+b)/c+(b+c)/a
=-b/b-c/c-a/a
=-3
(2)2x^2-3x-2=0
(2x+1)(x-...

全部展开

(1)a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a/b+a/c+b/c+b/a+c/a+c/b
=(a+c)/b+(a+b)/c+(b+c)/a
a+b+c=0
(a+c)/b+(a+b)/c+(b+c)/a
=-b/b-c/c-a/a
=-3
(2)2x^2-3x-2=0
(2x+1)(x-2)=0
x1=-0.5,x2=2
x1=-0.5,x^2+1/x^2=4.25
x1=2,x^2+1/x^2=4.25
(3)1/(1+a^2)+1/(1+b^2)
=(1+b^2)/ (1+a^2)(1+b^2)+(1+a^2)/(1+a^2)(1+b^2)
=(2+a^2+b^2)/[a^2+b^2+(ab)^2+1]
=(2+a^2+b^2)/(a^2+b^2+2)
=1

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