I made a table of squares. Starting from the bottom (44^2), I subtracted and looked for two squares that would fit the remainder. 44^2=1936. 1989-1936=53. 53=49+4. 44, 7, 2. I found that going down by twos worked. 42^2, 40^2, 38^2, etc. 42^2=1764. 1989-1764=225. Find two sqares that equal 225.
1 1
2 4
3 9
4 16
5 25
6 36
7 49
8 64
9 81
10 100
11 121
12 144
13 169
14 196
15 225
16 256
17 289
18 324
19 361
20 400
21 441
22 484
23 529
24 576
25 625
26 676
27 729
28 784
29 841
30 900
31 961
32 1024
33 1089
34 1156
35 1225
36 1296
37 1369
38 1444
39 1521
40 1600
41 1681
42 1764
43 1849
44 1936