100×100-99×99+98×98+...+2×2－1×1
=(100+99)(100-99)+(98+97)(98-97)+...+(2+1)(2-1)
=(100+99)+(98+97)+...+(2+1)
=5050
100X100—99X99+98X98+...+2X2—1X1
2个回答
相关问题
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