a)
[tex]U( 89^{37} + 88^{38} + 37^{39}) = [/tex]
[tex]= U( 89^{2 * 18 + 1} + 88^{4 * 9 + 2} + 37^{4*9+3}) =[/tex]
[tex]= U( 7921^{18}*89 + 59969536^{9} * 7744 + 1874161^{9} * 50653 ) =[/tex]
[tex]= U(1 * 9 + 6*4 + 1 * 3) = U(9 + 24 + 3) = U(36) = 6[/tex]
b)
[tex]U( 71^{10000001} ) = 1[/tex]
c)
[tex]U( 1009^{9001})= U( 1009^{2*4500 + 1}) = U( 1018081^{4500}*1009) = 1*9 = 9[/tex]
d)
[tex]U( 77^{36} + 77^{37} + 77^{38} + 77^{39})=[/tex]
[tex]= U[( 77^{36})( 77^{0} + 77^{1} + 77^{2} + 77^{3} )] =[/tex]
[tex]= U[( 77^{4*9})( 77^{0} + 77^{1} + 77^{2}77^{3})] =[/tex]
[tex]= U[(35153041^{9})(1 + 7 + 9 + 3)] = U[1*(20)] = U(20) = 0[/tex]