(35-12) * (35+12) = (35)(35) - (12)(12) 35 squared is....1,225 (quick trick...take all non-units digits and multiple it by its consecutive integer (in this case 3 * 4 = 12), then place the product in front of 25. e.g. 105 squared = 10 * 11 = 110, place it in front of 25 and get 11,025. 12 squared is...144 225-144 = 22-14 = 8 and 5 - 4 = 1, therefore 81 1,081