Explicație pas cu pas:
a)
[tex]( {2}^{4} ) {}^{7} - 2 {}^{28} = \\ = 2 {}^{4 \times 7} - {2}^{28} = \\ = {2}^{28} - {2}^{28} = \\ = 0[/tex]
b)
[tex]( {3}^{5} ) {}^{4} \div 3 {}^{19} = \\ = {3}^{5 \times 4} \div {3}^{19} = \\ = {3}^{20} \div {3}^{19} = \\ = 3 {}^{20 - 19} = \\ = {3}^{1} = \\ = 3[/tex]