Show that the cross-product terms formed from (Xi X), (Xj X), and (Xij Xi Xj + X) sum to
Chapter 9, Problem 9.4-4(choose chapter or problem)
Show that the cross-product terms formed from (Xi X), (Xj X), and (Xij Xi Xj + X) sum to zero, i = 1, 2, ... a and j = 1, 2, ... , b. Hint: For example, write a i=1 b j=1 (Xj X)(Xij Xi Xj + X) = b j=1 (Xj X) a i=1 [(Xij Xj) (Xi X)] and sum each term in the inner summation, as grouped here, to get zero.
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