In mathematics, a multiplicative inverse or reciprocal for a number x, denoted by 1/x is a number which when multiplied by x yields the multiplicative identity, 1
Ie, number*multiplicative inverse(number)=1
Multiplicative inverse (-1)=1/X=1/-1=-1
To check it (X* mul inverse(X)=1)
-1*-1=1
Hence it occurs