一道简算题,139*137/138+137*139/138=?

Question

一道简算题,
139*137/138+137*139/138=?

Answer 1

139*137/138+137*139/138
=(139*137+137*139)/138
=2(139*137)/138
=2(138+1)(138-1)/138
=2(138^2-1)/138
=(138^2-1)/69
=2*138-1/69
=19043/69