1 / ABC /（AB + BC + AC）= 1 / A + 1 / B + 1 / C
A + B / AB = 3 B + C / BC = 4 A + C / AC = 5
1 / A + 1 / B + 1 / C + 1 / B + 1 / A + 1 / C = 12
1 / A + 1 / B + 1 / C = 6
1 / ABC /（AB + BC + AC）= 1 / A + 1 / B + 1 / C = 6
BR> ABC /（AB + BC + AC）= 1/6 1 / ABC /（AB + BC + AC）= 1 / A + 1 / B + 1 / C
A + B / AB = 3 B + C / BC = 4 A + C / AC = 5
1 / A + 1 / B + 1 / C + 1 / B + 1 / A + 1 / C = 12
1 / A + 1 / B + 1 / C = 6
1 / ABC /（AB + BC + AC）= 1 / A + 1 / B + 1 / C = 6
BR> ABC /（AB + BC + AC）= 1/6