1道数学题100分!

ab/a+b=3
ca/c+a=4
bc/b+c=5

1/a+1/b=1/3
1/c+1/a=1/4
1/b+1/c=1/5

相加，
2(1/a+1/b+1/c)=47/60
1/a+1/b+1/c=47/120

ab+bc+ac/abc
=1/c+1/a+1/b
=47/120

原式是这样的吧！

ab/(a+b)=3
ca/(c+a)=4
bc/(b+c)=5

得：
(a+b)/ab=1/b+1/a=1/3
(c+a)/ca=1/a+1/c=1/4
(b+c)/bc=1/b+1/c=1/5

上面三式相加：

2(1/a+1/b+1/c)
=1/3+1/4+1/5
=(20+15+12)/60
=47/60

(ab+bc+ac)/abc

=1/a+1/b+1/c

=47/120

ab/a+b=3
ca/c+a=4
bc/b+c=5
每个式子取倒数得
(a+b)/ab=1/3
(a+c)/ac=1/4
(b+c)/bc=1/5
即
1/a+1/b=1/3
1/a+1/c=1/4
1/b+1/c=1/5
三式相加得
2(1/a+1/b+1/c)=47/60
所以1/a+1/b+1/c=47/120
即(ab+bc+ac)/abc=47/120

ab/a+b=3
ca/c+a=4
bc/b+c=5
ab+bc+ac/abc=
应该是
ab/(a+b)=3
ca/(c+a)=4
bc/(b+c)=5
(ab+bc+ac)/abc=
吧
ab/(a+b)=3
ca/(c+a)=4 <