3/4+5/8+5/16+6/32+7/64+8/128+9/256=?还有一道题:1/13×5+1/15×7+1/17×19+……+1/37×39=?
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/08 15:26:45
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3/4+5/8+5/16+6/32+7/64+8/128+9/256=?还有一道题:1/13×5+1/15×7+1/17×19+……+1/37×39=?
3/4+5/8+5/16+6/32+7/64+8/128+9/256=?
还有一道题:
1/13×5+1/15×7+1/17×19+……+1/37×39=?
3/4+5/8+5/16+6/32+7/64+8/128+9/256=?还有一道题:1/13×5+1/15×7+1/17×19+……+1/37×39=?
501/256
设:S=3/4+4/8+5/16+6/32+7/64+8/128+9/256
2S=3/2+1+5/8+3/8+7/32+1/8+9/128
2S-S=1+3/4+1/8+1/16+1/32+1/64+1/128-9/256
设:A=1+3/4+1/8+1/16+1/32+1/64+1/128-9/256
2A=2+3/2+1/4+1/8+1/16+1/32+1/64-9/128
2A-A=2-10/128+9/256
=2-11/256
=512/256-11/256
=501/256
还有一种方法式 数列的 估计你没学呢哎
第二题告诉你个方法
1/13*15 =1/13-1/15 都这样分解.然后相加
最后等于1/13+1/39=4/39