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GRE mathematics 1

Posted: Tue Sep 15, 2015 9:24 pm
by STATISTICS
Q1: How many different partial derivatives of order k are possible for a function f(x1,x2,....,xn) of n variables.
The answer is k-combinations of n+k-1.
Can anyone give an explanation in details?

Q2:The differential equation dp/dx=p(1-p)(p-2), possess the three equilibrium solutions p1=0, p2=1, p3=2, which of these are stable?
Also need an explanation in details........

Thanks for your replies.

Re: GRE mathematics 1

Posted: Tue Sep 15, 2015 10:25 pm
by BreakingBad
Regarding 1: This is a "Stars and Bars" application. See here: http://www.johndcook.com/blog/select_with_replacement/