题目看不太清楚,如果题目是
139*137/138+137*139/138
那么
=2*139*137/138
=2*(138+1)*(138-1)/138
=2*(138^2-1)/138
=2*138^2/138-2/138
=2*138-2/138
=276-1/69
=275又68/69
如果是
13.9*137/138+137*139/138
那么
=0.1*139*137/138+1*139*137/138
=1.1*139*137/138
=11/10*(138-1/138)
=1518/10-1/1380
=151又1103/1380