The multiplicative inverse of [1] is [1] because [1] ×[1] = [1].
The multiplicative inverse of [2] is [4] because
[2] ×[4] = [8] = [1] since we are working modulo 7.
Also the
multiplicative inverse of [4] is [2].
The multiplicative inverse of [3] is [5] because
[3] ×[5] = [15] = [1] since we are working modulo 7.
Also the
multiplicative inverse of [5] is [3].
The multiplicative inverse of [6] is [6] because [6] ×[6] = [36] = [1] since we are working modulo 7.