For the extension of the random-intercept linear mixed model (9.8) that assumes cov(????ij, ????ik) = ????2

???? ????|j−k|

, show that corr(yij, yik) = (

????2 u + ????|j−k|

????2

????

)

∕

(

????2 u + ????2

????

)

.