Question: Take a look at this here:

```
\documentclass[10pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
\begin{align*}
\Leftrightarrow \qquad P'_1(t)+\lambda P_1(t)&=\lambda e^{-\lambda t} && (2.6)\\
\Leftrightarrow \qquad e^{\lambda t}P'_1(t)+\lambda e^{\lambda t}P_1(t)&=\lambda e^{\lambda t} e^{-\lambda t}=\lambda \\
\end{align*}
\end{document}

```

Is it possible to have the equivalences below each other like the equations are?

```
\documentclass[10pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
\begin{alignat*}{4}
P'_1(t)&=-\lambda P_1(t)+\lambda P_0(t)\\
\Leftrightarrow &&\qquad  P'_1(t)+\lambda P_1(t)&=\lambda e^{-\lambda t} && (2.6)\\
\Leftrightarrow &&  e^{\lambda t}P'_1(t)+\lambda e^{\lambda t}P_1(t)&=\lambda e^{\lambda t} e^{-\lambda t}=\lambda \\
\end{alignat*}
\end{document}

```

This almost works but i have the mention problem that the first line is pulled to the very left.

Answer: 
Like so?

```
\documentclass{article}

\usepackage{amsmath}
\begin{document}
\begin{align}
\Leftrightarrow&& P'_1(t)+\lambda P_1(t)&=\lambda e^{-\lambda t} \tag{2.6} \\
\Leftrightarrow&& e^{\lambda t}P'_1(t)+\lambda e^{\lambda t}P_1(t)&=\lambda e^{\lambda t} e^{-\lambda t}=\lambda \notag
\end{align}
\end{document}

```

[![enter image description here](https://i.stack.imgur.com/82Cbm.png)](https://i.stack.imgur.com/82Cbm.png)
You can also use `alignat`:

[![enter image description here](https://i.stack.imgur.com/3UOxi.png)](https://i.stack.imgur.com/3UOxi.png)

Code:
-----

```
\documentclass[10pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\begin{document}
\begin{alignat*}{4}
  \Leftrightarrow &&\qquad P'_1(t)+\lambda P_1(t) &=\lambda e^{-\lambda t} && (2.6) \\
  \Leftrightarrow &&\qquad e^{\lambda t}P'_1(t)+\lambda e^{\lambda t}P_1(t) &=\lambda e^{\lambda t} e^{-\lambda t}=\lambda 
\end{alignat*}
\end{document}

```