Question

(7x^-1-y^-1)/(7x^-1+y^-1) если y/x=8^-1
даю 25 баллов!​

Answer 1

Ответ:

Объяснение:

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Answer 2

$\dfrac{7x^{-1}-y^{-1} }{7x^{-1}+y^{-1} }=\dfrac{\dfrac{7}{x} -\dfrac{1}{y} }{\dfrac{7}{x}+\dfrac{1}{y}} =\dfrac{(7y-x)\cdot xy}{xy\cdot (7y+x)}=\dfrac{7y-x}{7y+x}\\\\\dfrac{y}{x} =8^{-1} \\\\\dfrac{y}{x} =\dfrac{1}{8} \ \Rightarrow \ x=8y\\\\\dfrac{7y-x}{7y+x} =\dfrac{7y-8y}{7y+8y} =\dfrac{-y}{15y} =-\dfrac{1}{15}\\\\Otvet:\boxed{-\dfrac{1}{15}}$