Réponse :
Explications étape par étape :
Exercice 2 :
[tex]\left \{ {{10x-3y=35} \atop {5x-4y=-20}} \right.[/tex]
on multiplie la 2ème équation par -2 de façon à éliminer les x
[tex]\left \{ {{10x-3y=35} \atop {5x-4y=-20}} \right.\\\left \{ {{10x-3y=35} \atop {-2*5x-4y*-2=-20*-2}} \right. \\\left \{ {{10x-3y=35} \atop {-10x+8y=40}} \right. \\\left \{ {{10x-3y=35} \atop {5y=75}} \right. \\\left \{ {{10x-3y=35} \atop {y=\frac{75}{5} }} \right. \\\left \{ {{10x-3*15 =35} \atop {y=15} \right.\\\left \{ {{10x=35+45} \atop {y=15}} \right. \\\left \{ {{x=\frac{80}{10} } \atop {y=15}} \right. \\\left \{ {{x=8} \atop {y=15}} \right.[/tex]
2)
x = 8
y = 15
[tex]8(\frac{x-5}{y-5})=8(\frac{8-5}{15-5} )=8(\frac{3}{10})=\frac{24}{10} =\frac{12}{5} \\3(\frac{x+20}{y+20})=3(\frac{8+20}{15+20} )=3(\frac{28}{35}) = 3(\frac{4*7}{5*7})= 3(\frac{4}{5} )=\frac{12}{5}[/tex]
