A.各管段特性阻力數(shù)平方根之和 B.各管段特性阻力數(shù)平方根倒數(shù)之和 C.各管段特性阻力數(shù)平方根倒數(shù)之和的二次方 D.各管段特性阻力數(shù)平方根倒數(shù)之和的倒數(shù)的二次方
A.各管段特性阻力數(shù)倒數(shù)之和 B.各管段特性阻力數(shù)倒數(shù)之差 C.各管段特性阻力數(shù)之和 D.各管段特性阻力數(shù)之差
A.A B.X C.R D.D