To align several equations in Latex, I write a code like this:
\begin{alignat*}{7}
d &= \frac{1}{1 + 0.2316419x} & \quad & a_1 &= 0.31938153 & \quad & a_2 &= -0.356563782 \\
a_3 &= 1.781477937 & \quad & a_4 &= -1.821255978 & \quad & a_5 &= 1.330274429
\end{alignat*}
And I got something like this.

I don't understand why there is a space between a_1 and '='. Could you please tell me how to eliminate that space ? Thank you for your time.
