[tex]a) {17}^{28} = {17}^{14 \times 2} = { ({17}^{14} )}^{2} = > p.p[/tex]
[tex]b) {25}^{19} = {( {5}^{2} )}^{19} = { ({5}^{19} )}^{2} = > p.p[/tex]
[tex]c)1 + 3 + 5 + 7 + ... + 55[/tex]
[tex]1 + 3 + 5 + 7 + ... + 2n - 1 = {n}^{2} [/tex]
[tex]2n - 1 = 55 [/tex]
[tex]2n = 55 + 1[/tex]
[tex]2n = 56 \: | \div 2[/tex]
[tex]n = 28[/tex]
[tex] {n}^{2} = {28}^{2} = > p.p[/tex]
