11+13+15.+197+199
=100×100-5×5
=10000-25
=9975对不对?绝对正确为什么是100X100-5X5从1开始的连续奇数的和等于它们个数的平方1+3+5+……+197+199=100×1001+3+5+……+9=5×5所以11+13+15....+197+199=100×100-5×5=10000-25=9975
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