[tex] \frac{x}{4} = \frac{y}{5} =\ \textgreater \ 5x=4y =\ \textgreater \ x = \frac{4y}{5}
[/tex]
x*y = 500
[tex] \frac{4y}{5}* y = 500 =\ \textgreater \ 4y^{2} =2500 =\ \textgreater \ y^{2} = 625 =\ \textgreater \ [/tex] y = 25 sau y = -25
x = [tex] \frac{4y}{5} = \frac{4*25}{5} = 20 [/tex]
sau
x = [tex] \frac{4y}{5} = \frac{4* (-25)}{5} = -20 [/tex]
