+1859 If $a$ and $b$ are positive integers for which $ab - 3a + 4b = 13$, what is the minimal possible value of $|a - b|$?
+129771 ab - 3a + 4b = 13
ab + 4b = 13 + 3a
b ( a + 4) = 13 + 3a
b = (13 + 3a) / (a + 4)
a must be odd for b to be an integer
No integers avaiable
The function aproaches 3 when a is large
When a = 1 b = 16/ 5 = 3.2 = b
And any odd "a" > 1 will result in 3 < b < 4 (not an integer)
