Correct option is CGiven:Expression: 19+6+19−6\frac{1}{9 + \sqrt{6}} + \frac{1}{9 - \sqrt{6}}9+61+9−61Formula Used:1a+b+1a−b=2aa2−b2\frac{1}{a + b} + \frac{1}{a - b} = \frac{2a}{a^2 - b^2}a+b1+a−b1=a2−b22aSolution:19+6+19−6 =1(9+6)(9−6) =9−6+9+6(9)2−(6)2 =9+981−6 =1875=625\frac{1}{9 + \sqrt{6}} + \frac{1}{9 - \sqrt{6}} \\ \ \\ = \frac{1}{(9 + \sqrt{6})(9 - \sqrt{6})} \\ \ \\ = \frac{9 - \sqrt{6} + 9 + \sqrt{6}}{(9)^2 - (\sqrt{6})^2} \\ \ \\ = \frac{9 + 9}{81 -6} \\ \ \\ = \frac{18}{75} = \frac{6}{25}9+61+9−61 =(9+6)(9−6)1 =(9)2−(6)29−6+9+6 =81−69+9 =7518=256Final AnswerSo the correct answer is (c)