Suppose all the simple correlations between $x_i$ and $x_j$ are $r$ for all $i,j=1,2,\dots,p, i\neq j.p>8$. Find the partial correlation coefficient $r_{1p.2468}.$
By definition, $$r_{1p.2468}=\frac{cov(e_{1.2468},e_{p.2468})}{\sqrt{var(e_{1.2468})}\sqrt{var(e_{p.2468})}}$$ how can I find $cov(e_{1.2468},e_{p.2468}),var(e_{1.2468}),var(e_{p.2468})$ in terms of $r$?
