Question

初二上册数学题第八十一页第二题和第四题答案

Answer 1

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