[Tex/LaTex] How to align one equation with another multline equation

alignmultline

I have two equations: The first equation needs to be broken up over two lines (e.g., with multline) so that the rest of the equation is right aligned on the second line. I would like to have the second equation aligned with the first equation (i.e., their equal signs are aligned), but I can't seem to figure out how to align it and have the second part of the first equation be right justified.

Example 1: 

\documentclass[letterpaper,12pt]{article}
\usepackage{amsmath}
\begin{document}   
\begin{multline}
        \frac{dB}{dt} \approx  - 0.092409  \left(  22.2674  e^{-0.092409 t}+77.7326 e^{-0.0258637 t}  \right)
        \nonumber \\
        -\left( 200 \frac{\ln{\frac{1}{2}}}{26.8} \right) \exp{\left(\dfrac{\ln{\frac{1}{2}}}{26.8}t \right)}
        \nonumber \\
    \approx 2.057708e^{-0.092409 t}+7.18319e^{-0.0258637 t} 
\end{multline}
\end{document}

I put everything within multline environment, but the 2nd equation is not aligned with the first.
enter image description here

Example 2:

\documentclass[letterpaper,12pt]{article}
\usepackage{amsmath}
\begin{document}   
\begin{align}
        \frac{dB}{dt} &\approx  - 0.092409  \left(  22.2674  e^{-0.092409 t}+77.7326 e^{-0.0258637 t}  \right)
        \nonumber \\
        -\left( 200 \frac{\ln{\frac{1}{2}}}{26.8} \right) \exp{\left(\dfrac{\ln{\frac{1}{2}}}{26.8}t \right)}
        \nonumber \\
    &\approx 2.057708e^{-0.092409 t}+7.18319e^{-0.0258637 t} 
        \end{align}
\end{document}

Here, I've put everything in an aligned environment. The first equation and second equation are aligned, but the second part of the first equation is left aligned/justified. I would like it right justified and the first and third line left justified/aligned.

enter image description here

Best Answer

This doesn't really answer your question, but might solve your problem.

How about condensing the equation with constants? I threw in a macro \diff{}{} for differentials (which should be written with upright d's as it's an operator). Btw, there could be better choices for constants.

enter image description here

\documentclass[letterpaper,12pt]{article}
\usepackage{amsmath}

\newcommand{\diff}[2]{\frac{\mathrm{d}#1}{\mathrm{d}#2}}

\begin{document}   
  \begin{equation}
    \diff{B}{t} = a_1(b_1e^{c_1t}+b_2e^{-c_2t}) - \left(a_2\frac{\ln{\frac{1}{2}}}{b_3} \right) \exp \left(\frac{\ln{\frac{1}{2}}}{b_3}\right)
  \end{equation}
  %
  where the constants $a_i$, $b_i$, and $c_i$ are
  %
  \begin{align*}
    a_1 &= -0.092409, && a_2 = 200,     && \\
    b_1 &= 22.2674,   && b_2 = 77.7326,  && b_3 = 26.8, \\
    c_1 &= -0.092409, && c_2 = -0.0258637, &&
  \end{align*}
  %
  such that
  %
  \begin{equation}
    \diff{B}{t} \approx 2.057708e^{-0.092409 t}+7.18319e^{-0.0258637 t} 
  \end{equation}
\end{document}
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