2²/1×3+4²/3×5+6²/5×7+8²/7×9+...+20²
来源:学生作业帮 编辑:搜搜考试网作业帮 分类:数学作业 时间:2024/07/27 06:58:56
2²/1×3+4²/3×5+6²/5×7+8²/7×9+...+20²/19×20
![2²/1×3+4²/3×5+6²/5×7+8²/7×9+...+20²](/uploads/image/z/4619163-3-3.jpg?t=2%26%23178%3B%2F1%C3%973%2B4%26%23178%3B%2F3%C3%975%2B6%26%23178%3B%2F5%C3%977%2B8%26%23178%3B%2F7%C3%979%2B...%2B20%26%23178%3B)
题目有问题,按照规律,最后一个数应该是.+20²/19×21
2²/1×3+4²/3×5+6²/5×7+8²/7×9+...+20²/19×21
=4/1×3+16/3×5+36/5×7+64/7×9+...+400/19×21
=1+1/1×3+1+1/3×5+1+1/5×7+1+1/7×9+...+1+1/19×21
=1×10+1/2(1-1/3+1/3-1/5+1/5-.-1/21)
=10+1/2×20/21
=10又10/21
2²/1×3+4²/3×5+6²/5×7+8²/7×9+...+20²/19×21
=4/1×3+16/3×5+36/5×7+64/7×9+...+400/19×21
=1+1/1×3+1+1/3×5+1+1/5×7+1+1/7×9+...+1+1/19×21
=1×10+1/2(1-1/3+1/3-1/5+1/5-.-1/21)
=10+1/2×20/21
=10又10/21
2²/1×3+4²/3×5+6²/5×7+8²/7×9+...+20²
1²-2²+3²-4²+5²-6²+7²-8
(1-2²)+3²-4²+5²-6²+7²-8²+
2²/1*3+4²/3*5+6²/5*7+8²/7*9+10²/9*1
10²-9²+8²-7²+6²-5²+4²-3
2²/1×3+4²/3×5+6²/5×7+8²/7×9+……+2010²
3²/2×4+5²/4×6+7²/6×8+9²/8×10+11²/10
计算:3²/2×4+5²/4×6+7²/6×8+9²/8×10+11²
10²-9²+8²-7²+6²-5²+4²-3
10²-9²+8²-7²+6²-5²+4²-3
简便运算:10²-9²+8²-7²+6²-5²+4²
4²-1²=3*5,5²-2²=3*7,6²-3²=3*9,