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QBank 5: Q5.10

J

jensen

Member
In solution for part iv, when we differentiate the RHS of (iii) wrt x_i, what happened to the summands? Is this how we differentiate a summation?

Thanks.
 
Q&A Bank 5.10

When you write out the summation in full, you get terms in x(1), x(2), ..., x(n). When you differentiate wrt x(1), the only term giving a non-zero result is the first one, so we don't need a summation in the first term once we've differentiated.
 
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