Question

a+(1/b)=3 ,b+(1/a)=5 , найдите (a+b)/(a-b)=?​

Answer 1

$\left \{ {{a+\frac{1}{b}=3|*b} \atop {b+\frac{1}{a}=5|*a}} \right. \left \{ {{ab+1=3b} \atop {ab+1=5a}} \right. \Rightarrow 3b=5a \Leftrightarrow a=0.6b\\\frac{a+b}{a-b}=\frac{0.6b+b}{0.6b-b}=\frac{1.6a}{-0.4b}=-4$

Ответ: -4