What is the difference between multiplicative inverse and additive inverse?

Answer 1

The multiplicative inverse of a non-zero element, x, in a set, is an element, y, from the set such that x*y = y*x equals the multiplicative identity. The latter is usually denoted by 1 or I and the inverse of x is usually denoted by x-1 or 1/x. y need not be different from x. For example, the multiplicative inverse of 1 is 1, that of -1 is -1.

The additive inverse of an element, p, in a set, is an element, q, from the set such that p+q = q+p equals the additive identity. The latter is usually denoted by 0 and the additive inverse of p is denoted by -p.

Answer 2

The additive inverse is the inverse under addition; the multiplicative inverse is the inverse under multiplication. For example, the additive inverse of any real or complex number is its negative: the inverse of 3 is -3 and vice versa. The multiplicative inverse of a number other than 0 (which has no such inverse) is its reciprocal: the inverse of 2 is 1/2, and vice versa. Adding a number and its additive inverse gives the additive identity, 0. Multiplying a number by its multiplicative inverse gives the multiplicative identity, 1.