a = {[1,(5)] la patrat - [0,(5)] la patrat } • 9/19
[tex] = [( {1 \frac{5}{9})}^{2} - { (\frac{5}{9} )}^{2} ] • \frac{9}{19} \\ = [( { \frac{9 \times 1 + 5}{9})}^{2} - { (\frac{5}{9} )}^{2} ] • \frac{9}{19} \\ = [( {\frac{14}{9})}^{2} - { (\frac{5}{9} )}^{2} ] • \frac{9}{19} \\ = ( { \frac{ {14}^{2} }{ {9}^{2} }} - { \frac{ {5}^{2} }{ {9}^{2} } )}^{} • \frac{9}{19} [/tex]
[tex]\\ = \frac{196 - 25}{81} \times \frac{9}{19} \\ = \frac{171}{81} \times \frac{9}{19} \\ = \frac{9}{9} \times \frac{1}{1} = \\ = 1 \times 1 \\ = 1[/tex]
