Question

Encontrar a soluça do sistema

Answer 1

Bom dia.

Vamos chamar de:
1/x = a 
1/y = b

$\left \{ {{5/x - 3/y=-1} \atop {15/x + 7/y=5}} \right. \\ \\ \left \{ {{5a - 3b=-1(-3)} \atop {15a + 7b=5}} \right. (+) \\ \\ \left \{ {{-15a +9b=3} \atop {15a + 7b=5}} \right. \\ \\ 15a-15a+9b+7b=3+5 \\ 16b=8 \\ b=1/2=1/y \\ y=2 \\ \\ 5a=3b-1 \\ 5a=3/2-1 \\ 5a=1/2 \\ a=1/10=1/x \\ x=10$

∴ S = {(10, 2)}