Question

rezolvati e xercitiul 15

Answer 1

[tex] \left \{ {{2x+3y=21|*2\ \textless \ =\ \textgreater \ 4x+6y=42} \atop {7x-2y=11}|*3\ \textless \ =\ \textgreater \ 21x-6y=33} \right. \\ ------------\\ 25x=75\\ x=3\\\\ 2*3+3y=21=\ \textgreater \ 6+3y=21=\ \textgreater \ 3y=15=\ \textgreater \ y=5\\\\ a) \frac{x}{y} = \frac{3}{5} \\ b) \frac{x+y}{x-y} = \frac{8}{-2} \\\\ Proba: \frac{2x+3y}{7x-2y} = \frac{21}{11} \\ =\ \textgreater \ (2*3+3*5)*11=(7*3-2*5)*21\\ =\ \textgreater \ (15+6)*11=(21-10)*21\\ =\ \textgreater \ 21*11=11*21\\ =\ \textgreater \ 231=231[/tex]