若a+b+c=0,且abc≠0,求a(1/b+1/c)+b(1/a+1/c)+c(1/a+1/b)的值1.若a+b+c=0,且abc≠0,求a(1/b+1/c)+b(1/a+1/c)+c(1/a+1/b)的值2.已知x、y、z满足x+1/y=4,y+1/z=1,z+1/x=7/3,求xyz的值.
若a+b+c=0,且abc≠0,求a(1/b+1/c)+b(1/a+1/c)+c(1/a+1/b)的值
1.若a+b+c=0,且abc≠0,求a(1/b+1/c)+b(1/a+1/c)+c(1/a+1/b)的值
2.已知x、y、z满足x+1/y=4,y+1/z=1,z+1/x=7/3,求xyz的值.
1.
a(1/b+1/c)+b(1/a+1/c)+c(1/a+1/b)
=a/b+a/c+b/a+b/c+c/a+c/b
=(b+c)/a+(a+c)/b+(a+b)/c
=-a/a-b/b-c/c
=-1-1-1
=-3
2.
∵x+1/y=4 ∴x=(4y-1)/y
∵y+1/z=1 ∴z=1/(1-y)
z+1/x=7/3
∴1/(1-y)+y/(4y-1)=7/3
y=2/5
∴x=3/2,z=5/3
∴xyz=3/2*2/5*5/3
=1
12
∵a+b+c=0;
∴(a+b+c)(a+b+c)=a*a+b*b+c*c+2ab+2ac+2bc=0;
∴2ab+2ac+2bc=0
∴①=0/abc
=0
是0!!!!!!!!!!!!!!!!11
1)
a(1/b+1/c)+b(1/a+1/c)+c(1/a+1/b)
=a(b+c)/bc+b(a+c)/ac+c(a+b)/ab
=-a^2/bc-b^2/ac-c^2/ab
=-(a^3+b^3+c^3)/abc
=-[(a^3+b^3+c^3-3abc)/abc+3abc/abc]
=-[(a+b+c)(a^2+b^2+c^2-ab-bc-ca)/abc+3]
=-[0+3]
=-3
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(b+c)+b(a+c)+c(a+b)]/abc =(2ab+2ac+2bc)/abc.① ∵a+b+c=0; ∴(a+b+c)(a+b+c)=a*a+b*b+c*c+2ab+2ac+2bc=0; ∴2ab+2ac+2bc=0 ∴①=0/abc =02.(X+1/Y...
你是错的真确的
a(1/b+1/c)+b(1/c+1/a)+c(1/a+1/b)
=a(1/a+1/b+1/c) + b(1/b+1/c+1/a) + c(1/c+1/a+1/b) -3
=(a+b+c)*(1/a+1/b+1/c)-3
=-3
好难