原式=(1/2)(1/2-1/4+1/3-1/5+1/4-1/6+...+1/11-1/13)
=(1/2)(1/2+1/3-1/12-1/13)
=(1/2)(5/12+10/39)
=(1/2)(65/156+40/156)
=105/312;
=35/104;
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原式=(1/2)(1/2-1/4+1/3-1/5+1/4-1/6+...+1/11-1/13)
=(1/2)(1/2+1/3-1/12-1/13)
=(1/2)(5/12+10/39)
=(1/2)(65/156+40/156)
=105/312;
=35/104;
很高兴为您解答,skyhunter002为您答疑解惑
如果本题有什么不明白可以追问,