Timeout after 10.0m

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\[\frac{-\left(f + n\right)}{f - n}\]

\frac{-\left(f + n\right)}{f - n}

double code(double f, double n) {
	return (-(f + n) / (f - n));
}

Reproduce

herbie shell --seed 2020091 
(FPCore (f n)
  :name "subtraction fraction"
  :precision binary64
  (/ (- (+ f n)) (- f n)))