Wide equations and fleqn left margin alignment

Question

Is it possible to force Latex to maintain the left margin for wide equations?

I have a document with fleqn option enabled to left align all equations. If the equation is longer than available space LaTeX moves the equation left and, if this does not yield enough space, moves the equation tag to the next line. I would like to force LaTeX to always maintain the left margin even if the equations are longer than available space. I would like to enforce this in the entire document, even at a cost of violating the right margin. Is there any way to achieve this?

MWE:

\documentclass{article}
\usepackage[fleqn]{amsmath}
\begin{document}

What I have now:
\begin{equation}
    f(x) = x^2
\end{equation}
\begin{equation}
    f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16}
\end{equation}
\begin{equation}
    f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16} + x^{17}
\end{equation}
\begin{equation}
    f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16} + x^{17} + x^{18}
\end{equation}

What I want:
\begin{equation}
    f(x) = x^2
\end{equation}
\begin{equation}
    \qquad\,\, f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16}
\end{equation}
\begin{equation}
    \qquad\,\,\, f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16} + x^{17}
\end{equation}
\begin{equation}
    \qquad\,\,\,f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16} + x^{17} + x^{18}
\end{equation}
\end{document}

Answer 1

I'd break the long terms. Anyway, you're the ultimate judge.

Use gather.

\documentclass{article}
\usepackage[fleqn]{amsmath}

\begin{document}

\begin{equation}
0=0
\end{equation}
Now let's see the result
\begin{gather}
  f(x) = x^2
\\
  f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10} 
       + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16}
\\
  f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10}
       + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16} + x^{17}
\end{gather}
It also works for a single equation
\begin{gather}
  f(x) = x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + x^{10}
       + x^{11} + x^{12} + x^{13} + x^{14} + x^{15} + x^{16} + x^{17} + x^{18}
\end{gather}

\end{document}