用简便方法计算.5/12+7/15+8/15+7/12=、1--3/7--2/7=、3/4+8/14--1/4--1/14=、5/8+1/3--1/8+2/3=
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![用简便方法计算.5/12+7/15+8/15+7/12=、1--3/7--2/7=、3/4+8/14--1/4--1/14=、5/8+1/3--1/8+2/3=](/uploads/image/z/68540-68-0.jpg?t=%E7%94%A8%E7%AE%80%E4%BE%BF%E6%96%B9%E6%B3%95%E8%AE%A1%E7%AE%97.5%2F12%2B7%2F15%2B8%2F15%2B7%2F12%3D%E3%80%811--3%2F7--2%2F7%3D%E3%80%813%2F4%2B8%2F14--1%2F4--1%2F14%3D%E3%80%815%2F8%2B1%2F3--1%2F8%2B2%2F3%3D)
用简便方法计算.5/12+7/15+8/15+7/12=、1--3/7--2/7=、3/4+8/14--1/4--1/14=、5/8+1/3--1/8+2/3=
用简便方法计算.5/12+7/15+8/15+7/12=、1--3/7--2/7=、3/4+8/14--1/4--1/14=、5/8+1/3--1/8+2/3=
用简便方法计算.5/12+7/15+8/15+7/12=、1--3/7--2/7=、3/4+8/14--1/4--1/14=、5/8+1/3--1/8+2/3=
5/12+7/15+8/15+7/12
=(5/12+7/12)+(7/15+8/15)
=1+1
=2
1--3/7--2/7
=1-(3/7+2/7)
=1-5/7
=2/7
3/4+8/14--1/4--1/14
=(3/4-1/4)+(8/14-1/14)
=1/2+1/2
=1
5/8+1/3--1/8+2/3
=(5/8-1/8)+(1/3+2/3)
=1/2+1
=1又1/2