如果a²-b²=(a+b)*(a-b),那么,20²-19²+18²-17²+...+2²-1²简便运算啊~~急啊~~
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![如果a²-b²=(a+b)*(a-b),那么,20²-19²+18²-17²+...+2²-1²简便运算啊~~急啊~~](/uploads/image/z/201405-21-5.jpg?t=%E5%A6%82%E6%9E%9Ca%26%23178%3B-b%26%23178%3B%3D%28a%2Bb%29%2A%28a-b%29%2C%E9%82%A3%E4%B9%88%2C20%26%23178%3B-19%26%23178%3B%2B18%26%23178%3B-17%26%23178%3B%2B...%2B2%26%23178%3B-1%26%23178%3B%E7%AE%80%E4%BE%BF%E8%BF%90%E7%AE%97%E5%95%8A%7E%7E%E6%80%A5%E5%95%8A%7E%7E)
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如果a²-b²=(a+b)*(a-b),那么,20²-19²+18²-17²+...+2²-1²简便运算啊~~急啊~~
如果a²-b²=(a+b)*(a-b),那么,20²-19²+18²-17²+...+2²-1²
简便运算啊~~急啊~~
如果a²-b²=(a+b)*(a-b),那么,20²-19²+18²-17²+...+2²-1²简便运算啊~~急啊~~
=(20+19)*(20-19)+(18+17)*(18-17)+.+(2+1)(2-1)
=20+19+18+17+.+2+1
=(20+1)*10
=210