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Problem
Squaring numbers like 48 or 52 requires long multiplication.
Solution
Use (50-a)² = 2500 - 100a + a² or (50+a)² = 2500 + 100a + a²
Benefit
Converts difficult squares into simple arithmetic around 2500.
Example
48² (50-2):
2500 - 200 + 4 = 2304
52² (50+2):
2500 + 200 + 4 = 2704
47² (50-3):
2500 - 300 + 9 = 2209