A stretch of desert is populated by two species of animals, roadrunners and coyotes, who are engaged in an endless game of rivalry and mischief. The populations and of roadrunners and coyotes years from now can be modelled by
If there are 310 roadrunners and 200 coyotes initially (at time ), find according to this model.
If you come to the conclusion that no such (finite) limit exists, enter 666.
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First, homogenize the dynamics by translating the state-variables appropriately, i.e. find real α , β such that with the substitution r ( t ) = r ′ ( t ) + α and c ( t ) = c ′ ( t ) + β , the constant part on the right hand side vanishes. Thus, we require α = 0 . 8 α − 0 . 7 β + 2 0 0 , β = 0 . 7 α + 0 . 8 β − 1 7 0 Solving this, we get α = 3 0 0 , β = 2 0 0 . With the new state-variables ( r ′ ( t ) , c ′ ( t ) ) , by direct substitution, we have r ′ ( t + 1 ) 2 + c ′ ( t + 1 ) 2 = 1 . 1 3 ( r ′ ( t ) 2 + c ′ ( t ) 2 ) with r ′ ( 0 ) = 1 0 , c ′ ( 0 ) = 0 . Thus it is clear that the limit diverges.