1. The problem statement, all variables and given/known data Groups G and H are both groups in Z_7 (integer modulo), the mapping Is given by ø(g) = 2g is ø: G-->H a homomorphism? 3. The attempt at a solution My textbook says yes, I can't understand why. ø(g1g2) = 2(g1g2) does not equal 2g1*2g2 = ø(g1)ø(g2) something missing here?