c₂m₂·(t - t₂)+c₁m₁·(t - t₁) = 0
c₂m₂t - c₂m₂t₂ + c₁m₁t - c₁m₁t₁ = 0
c₁m₁t + c₂m₂t = c₁m₁t₁ + c₂m₂t₂
t·(c₁m₁ + c₂m₂) = c₁m₁t₁ + c₂m₂t₂
t = c₁m₁t₁+c₂m₂t₂ / c₁m₁+c₂m₂
c₂m₂·(t - t₂)+c₁m₁·(t - t₁) = 0
c₂m₂t - c₂m₂t₂ + c₁m₁t - c₁m₁t₁ = 0
c₁m₁t + c₂m₂t = c₁m₁t₁ + c₂m₂t₂
t·(c₁m₁ + c₂m₂) = c₁m₁t₁ + c₂m₂t₂
t = c₁m₁t₁+c₂m₂t₂ / c₁m₁+c₂m₂