20²-19²+18²-17²+16²-15²+2²-1²=简便运算-_-|||打错了20²-19²+18²-17²+16²-15²+……+2²-1²=
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/17 15:58:31
![20²-19²+18²-17²+16²-15²+2²-1²=简便运算-_-|||打错了20²-19²+18²-17²+16²-15²+……+2²-1²=](/uploads/image/z/201404-20-4.jpg?t=20%26%23178%3B%EF%BC%8D19%26%23178%3B%2B18%26%23178%3B%EF%BC%8D17%26%23178%3B%2B16%26%23178%3B%EF%BC%8D15%26%23178%3B%2B2%26%23178%3B%EF%BC%8D1%26%23178%3B%3D%E7%AE%80%E4%BE%BF%E8%BF%90%E7%AE%97-_-%7C%7C%7C%E6%89%93%E9%94%99%E4%BA%8620%26%23178%3B%EF%BC%8D19%26%23178%3B%2B18%26%23178%3B%EF%BC%8D17%26%23178%3B%2B16%26%23178%3B%EF%BC%8D15%26%23178%3B%2B%E2%80%A6%E2%80%A6%2B2%26%23178%3B%EF%BC%8D1%26%23178%3B%3D)
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20²-19²+18²-17²+16²-15²+2²-1²=简便运算-_-|||打错了20²-19²+18²-17²+16²-15²+……+2²-1²=
20²-19²+18²-17²+16²-15²+2²-1²=
简便运算
-_-|||打错了
20²-19²+18²-17²+16²-15²+……+2²-1²=
20²-19²+18²-17²+16²-15²+2²-1²=简便运算-_-|||打错了20²-19²+18²-17²+16²-15²+……+2²-1²=
20²-19²+18²-17²+16²-15²+.+2²-1²
=(20+19)(20-19)+(18+17)(18-17)+(16+15)(16-15)+.+(2+1)(2-1)
=20+19+18+17+.+2+1
=(20+1)×20÷2
=210