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1/2*4+1/4*6+1/6*8+1/8*10+1/10*12+1/12*14
题目详情
1/2*4+1/4*6+1/6*8+1/8*10+1/10*12+1/12*14
▼优质解答
答案和解析
1/2*4+1/4*6+1/6*8+1/8*10+1/10*12+1/12*14
=(1/2)(2/2*4+2/4*6+2/6*8+2/8*10+2/10*12+2/12*14)
=(1/2)(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12+1/12-1/14)
=(1/2)(1/2-1/14)
=3/14
=(1/2)(2/2*4+2/4*6+2/6*8+2/8*10+2/10*12+2/12*14)
=(1/2)(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12+1/12-1/14)
=(1/2)(1/2-1/14)
=3/14
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