1。 The above does not have to be multiplied, but it can also be115 =115 (1+5)+5/15 (1+5). Put forward a115 =115 [(1+5)] on both sides of the above formula. It is not difficult to see from the above formula that it is only multiplied by a 1. However, in the two parts, a molecule must be two factors (3,5) of11+3,3/1+3 and11+5,5.

2。 Subtraction analysis method is the same, except that after subtraction, the numerator is the same as the denominator, that is, it is multiplied by a 1, and the number to be subtracted must be two of them (if I can't remember clearly, I will use my own factor, the factor of 15 is 5 and 3, the factor of 6 is 2 and 3, and the factor of 3 is 3 and 1. . . ) greatly reduced.

115 =115 [5/(5-3)-3/(5-3)] Pay attention to the positions of 5 and 3 on the molecule.

I feel that the expression is not good enough, but I hope you can pick up your pen and read it again according to my thinking, which should be understandable.