.
From = 24 we have
= = 576
(h-a)*(h+a) = 576.
The divisors of the number 576 are the numbers
1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 32, 36, 48, 64, 72, 96, 144, 192, 288, 576.
Therefore, we have the series of cases.
1) h - a = 1
h + a = 576
------------------ > no solution in integer positive numbers.
2) h - a = 2
h + a = 288
------------------ > h = = 145; a = 145-2 = 143.
3) h - a = 3
h + a = 192
------------------ > no solution in integer positive numbers.
4) h - a = 4
h + a = 144
------------------ > h = = 74; a = 74-4 = 70.
Moving in this way further along the row of divisors of the number 576 till the number h = 18 inclusive,
you will consider all the cases and will get all other possible (and/or impossible) solutions.
Since I don't want to deprive you this joy, I will leave you at this point.