20²-19²+18²-17²+16²-15²+.+2²-1²要简便 要写简便过程
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/17 17:07:03
![20²-19²+18²-17²+16²-15²+.+2²-1²要简便 要写简便过程](/uploads/image/z/201407-23-7.jpg?t=20%26%23178%3B-19%26%23178%3B%2B18%26%23178%3B-17%26%23178%3B%2B16%26%23178%3B-15%26%23178%3B%2B.%2B2%26%23178%3B-1%26%23178%3B%E8%A6%81%E7%AE%80%E4%BE%BF+%E8%A6%81%E5%86%99%E7%AE%80%E4%BE%BF%E8%BF%87%E7%A8%8B)
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20²-19²+18²-17²+16²-15²+.+2²-1²要简便 要写简便过程
20²-19²+18²-17²+16²-15²+.+2²-1²要简便 要写简便过程
20²-19²+18²-17²+16²-15²+.+2²-1²要简便 要写简便过程
=(20+19)(20-19)+(18+17)(18-17)+(16+15)(16-15)+.+(2+1)(2-1)
=39+35+31+.3
=(39+3)×10÷2
=42×5
=210
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