How may I reduce horizontal space between the two equations of the following?

Question

The spacing is too much; I want some space between the equations, but not as much space as of the following. I would appreciate if someone could provide me with a coherent answer.

    \documentclass[11pt,a4paper]{article}
    \usepackage{blindtext}
    \usepackage{mathtools}
    \DeclareMathOperator{\sgn}{sgn}
\begin{document}
\begin{flalign*}
&+(+a)=+a,& &-(+a)=-a&\\
&+(-a)=-a,& &-(-a)=+a&
\end{flalign*}
\end{document}

Answer 1

Not sure what will best meet your criterion of "not as much space" being taken between the two columns of equations. The following solution may fit the bill. It also results, incidentally, in better centering of the material -- which I take to be a criterion as well.

\documentclass[11pt,a4paper]{article}
\usepackage{amsmath}
\begin{document}
\begin{align*}
+(+a)&=+a,& -(+a)&=-a\\
+(-a)&=-a,& -(-a)&=+a
\end{align*}
\end{document}

Answer 2

With alignat you control the space by yourself.

\documentclass[11pt,a4paper]{article}
\usepackage{mathtools}
\DeclareMathOperator{\sgn}{sgn}
\begin{document}
\begin{alignat*}{2}
+(+a)&=+a,& \qquad -(+a)&=-a\\
+(-a)&=-a,&       -(-a)&=+a
\end{alignat*}
\begin{alignat*}{2}
+(+a)&=+a,& \hspace{1in} -(+a)&=-a\\
+(-a)&=-a,&       -(-a)&=+a
\end{alignat*}
\end{document}