Răspuns:
Dacă pot fi scrise sub formă de a^2, sunt pătrate perfecte.
[tex]16 \times 25 = {2}^{4} \times {5}^{2} = ( {2}^{2} \times 5)^{2} pp[/tex]
[tex] {2}^{18} \times {3}^{6} = ( {2}^{9} \times {3}^{3} )^{2} pp[/tex]
[tex] {5}^{2} \times {3}^{18} = ( {3}^{9} \times 5)^{2} pp[/tex]
[tex] {2}^{4} \times {10}^{2} = ( {2}^{2} \times 10)^{2} pp[/tex]
[tex]( {2}^{2} )^{15} = ( {2}^{15} )^{2} [/tex]
[tex]( {11}^{2} )^{17} = ( {11}^{17} )^{2} = > inmultirea \: este \: pp[/tex]
[tex] {5}^{14} \times {7}^{8} \times {13}^{24} = ( {5}^{7} \times {7}^{4} \times {13}^{12} )^{2} pp[/tex]
[tex] {3}^{25} + {3}^{24} = {3}^{24}(3 + 1) = {3}^{24} \times {2}^{2} = (2 \times {3}^{12} )^{2} pp[/tex]
[tex] {2}^{25} - 7 \times {2}^{20} = {2}^{20} ( {2}^{5} - 7) = {2}^{20} (32 - 7) = {2}^{20} \times {5}^{2} = ( {2}^{10} \times 5)^{2} pp[/tex]
