. Example: [R-103, * and K-1, 13; *] are groups. 1x>0 p(x) Kerq={x|x>0,x∈R} -1x<0Example: [R-{0};*] and [{-1,1};*] are groups.    −   = 1 0 1 0 ( ) x x  x Ker ={x | x  0, xR}