(1又3/4-8/7-12/7)÷(-8/7)
= -7/4x7/8+8/7x7/8+12/7x7/8
=-49/32+1+3/2
=-49/32+48/32
=-1/32
所以
原式=-1/32-32=-32又1/32
(1又3/4-8/7-12/7)÷(-8/7)+(-8/7)÷(1又3/4-8/7-12/7)
=(7/4-20/7)÷(-8/7)+(-8/7)÷(7/4-20/7)
=(-31/28)(-7/8)+(-8/7)(-28/31)
=31/32+32/31
=1985/992
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