ความคิดเห็นที่ 4
1. 24 x 26 = (25-1) x (25+1) = (25)^2 - (1)^2 = 625 - 1 = 624
2. 18 x 12 = (15+3) x (15-3) = (15)^2 - (3)^2 = 225 - 9 = 216
a^2 - b^2 = (a+b) x (a-b)
15 x 15 = 1x2....5x5 = 2.....25 =225
25 x 25 = 2x3....5x5 = 6.....25 =625
35 x 35 = 3x4....5x5 = 12.....25 =1225
45 x 45 = 4x5....5x5 = 20.....25 =2025
104 x 104 = (100)^2 + 2x(100)x(4) + (4)^2 = 10,000 + 800 + 16 = 10,816
96 x 96 = (100)^2 - 2x(100)x(4) + (4)^2 = 10,000 - 800 + 16 = 9,216
(a+b)^2 = a^2 + 2ab + b^2
จากคุณ :
Waterman (LN106) 
- [
7 มิ.ย. 50 20:59:52
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