简算4/5*7+4/7*9+4/9*11+.+4/53*55=?
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![简算4/5*7+4/7*9+4/9*11+.+4/53*55=?](/uploads/image/z/108078-6-8.jpg?t=%E7%AE%80%E7%AE%974%2F5%2A7%2B4%2F7%2A9%2B4%2F9%2A11%2B.%2B4%2F53%2A55%3D%3F)
简算4/5*7+4/7*9+4/9*11+.+4/53*55=?
简算4/5*7+4/7*9+4/9*11+.+4/53*55=?
简算4/5*7+4/7*9+4/9*11+.+4/53*55=?
4/5*7+4/7*9+4/9*11+.+4/53*55
=2(1/5-1/7+1/7-1/9+……+1/53-1/55)
=2(1/5-1/55)
=4/11
4/5*7+4/7*9+4/9*11+....+4/53*55
=2(1/5-1/7+1/7-1/9+……+1/53-1/55)
=2(1/5-1/55)
=4/11