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Mathematics

The roots of the equation x+1xx + \dfrac{1}{x} = 3 are:

  1. 2±52\dfrac{2 \pm \sqrt{5}}{2}

  2. 3±52\dfrac{3 \pm \sqrt{5}}{2}

  3. 1±32\dfrac{1 \pm \sqrt{3}}{2}

  4. none of these

Quadratic Equations

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Answer

Given,

x+1xx + \dfrac{1}{x} = 3

Multiplying whole equation by x, we get:

x2+1x=3\Rightarrow \dfrac{x^2 + 1}{x} = 3

⇒ x2 + 1 = 3x

⇒ x2 - 3x + 1 = 0

Comparing equation x2 - 3x + 1 = 0 with ax2 + bx + c = 0, we get :

a = 1, b = -3 and c = 1.

By formula,

x = b±b24ac2a\dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Substituting values we get :

x=(3)±(3)24×1×12×1=3±942=3±52.\Rightarrow x = \dfrac{-(-3) \pm \sqrt{(-3)^2 - 4 \times 1 \times 1}}{2 \times 1} \\[1em] = \dfrac{3 \pm \sqrt{9 - 4}}{2} \\[1em] = \dfrac{3 \pm \sqrt{5}}{2}.

Hence, option 2 is the correct option.

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