One of the normal equations for fitting a straight line \(y=a+bx\) is
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Normal equations for the regression line
\[
\boxed{
y=a+bx
}
\]
are
\[
\boxed{
\begin{aligned}
\sum y &= na+b\sum x,[2mm]
\sum xy &= a\sum x+b\sum x^2.
\end{aligned}
}
\]