Question

Se (x^-1 + y^-1)^-1 = 2, então y é igual a: a) x/1-2x b) -x/1-2x c) 2x/x-2 d) x-2/2x e) x/1+x

Answer 1

 (x^-1 + y^-1)^-1 = 2

(1/x + 1/y)^-1 = 2

1/(1/x +1/y) = 2

2/x + 2/y =1

2/y = 1 - 2/x

2/y = (x -2)/x

y(x -2) = 2x

y = 2x/(x -2)

R: c)