666 + 987 * 654 / 987 * 655-321 how to operate easily, and the meaning of each step also need to be improved (1 / 123456788-123456789) △ 1 / 123456788 + 1 / 123456789) the same thing

987 * 655-321 of 666 + 987 * 654
=987*655-321/666+987*654
=987*（654+1）-321/666+987*654
=987*654+987-321/666+987*654
=987*654+666/666+987*654
=1
Methods: the difference between the numerator and 654 and 655 in the denominator is only 1. Change 655 into (654 + 1) or 654 into (655-1), so that the numerator denominator can be approximately divided

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