f(x) varies inversely with x and f(x)=−10 when x = 20. What is the inverse variation equation? Responses f(x)=−2x f ( x ) = − 2 x f(x)=−5x f ( x ) = − 5 x f(x)=−200x f ( x ) = − 200 x f(x)=−0.5x f ( x ) = − 0.5 x