Question 58

If $$x+\frac{1}{9x}=4$$, then $$9x^2+\frac{1}{9x^2}$$ the value is

Solution

Given : $$x+\frac{1}{9x}=4$$

Multiplying both sides by 3,

=> $$3x+\frac{1}{3x}=12$$

Squaring both sides, we get :

=> $$(3x+\frac{1}{3x})^2=(12)^2$$

=> $$9x^2+\frac{1}{9x^2}+2(3x)(\frac{1}{3x})=144$$

=> $$9x^2+\frac{1}{9x^2}=144-2=140$$

=> Ans - (B)

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