1) 1921 = (20-1)(20+1) = 400 - 1 = 3992) 2832 = (30-2)(30+2) = 900 - 4 = 8963) 109111 = (110-1)(110+1) = 12100 - 1 = 120994) 1.51.7 = (1.6-0.1)(1.6+0.1) = 2.56 - 0.01 = 2.55
1) 1921 = (20-1)(20+1) = 400 - 1 = 399
2) 2832 = (30-2)(30+2) = 900 - 4 = 896
3) 109111 = (110-1)(110+1) = 12100 - 1 = 12099
4) 1.51.7 = (1.6-0.1)(1.6+0.1) = 2.56 - 0.01 = 2.55