MathDB

We consider the set of four-digit positive integers

x =\overline{abcd}

with digits different than zero and pairwise different. We also consider the integers

y = \overline{dcba}

and we suppose that

x > y

. Find the greatest and the lowest value of the difference

x-y

, as well as the corresponding four-digit integers

x,y

for which these values are obtained.

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