1951 AMC 12 Question 20
AMC12 · 1951 AMC 12
When simplified and expressed with negative exponents, the expression $(x+y)^{-1}(x^{-1}+y^{-1})$ is equal to:
$x^{-2}+2x^{-1}y^{-1}+y^{-2}$
$x^{-2}+2^{-1}x^{-1}y^{-1}+y^{-2}$
$x^{-1}y^{-1}$
$x^{-2}+y^{-2}$
$\dfrac{1}{x^{-1}y^{-1}}$