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If alpha and beta are the roots of equat...

If `alpha and beta` are the roots of equation `6x^(2)+x-2=0`, find the value of `(alpha)/(beta)+(beta)/(alpha)`:

A

`-(25)/(12)`

B

`-(12)/(75)`

C

`-(4)/(9)`

D

none of these

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The correct Answer is:
To solve the problem, we need to find the value of \(\frac{\alpha}{\beta} + \frac{\beta}{\alpha}\) where \(\alpha\) and \(\beta\) are the roots of the quadratic equation \(6x^2 + x - 2 = 0\). ### Step 1: Identify the coefficients of the quadratic equation The given quadratic equation is in the form \(ax^2 + bx + c = 0\). Here, we have: - \(a = 6\) - \(b = 1\) - \(c = -2\) ### Step 2: Calculate the sum and product of the roots Using Vieta's formulas: - The sum of the roots \(\alpha + \beta = -\frac{b}{a} = -\frac{1}{6}\) - The product of the roots \(\alpha \beta = \frac{c}{a} = \frac{-2}{6} = -\frac{1}{3}\) ### Step 3: Express \(\frac{\alpha}{\beta} + \frac{\beta}{\alpha}\) We can rewrite \(\frac{\alpha}{\beta} + \frac{\beta}{\alpha}\) as: \[ \frac{\alpha^2 + \beta^2}{\alpha \beta} \] ### Step 4: Calculate \(\alpha^2 + \beta^2\) Using the identity: \[ \alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta \] Substituting the values we found: \[ \alpha^2 + \beta^2 = \left(-\frac{1}{6}\right)^2 - 2\left(-\frac{1}{3}\right) \] Calculating: \[ = \frac{1}{36} + \frac{2}{3} \] To add these fractions, we convert \(\frac{2}{3}\) to have a common denominator of 36: \[ \frac{2}{3} = \frac{2 \times 12}{3 \times 12} = \frac{24}{36} \] Thus: \[ \alpha^2 + \beta^2 = \frac{1}{36} + \frac{24}{36} = \frac{25}{36} \] ### Step 5: Substitute back to find \(\frac{\alpha}{\beta} + \frac{\beta}{\alpha}\) Now we substitute \(\alpha^2 + \beta^2\) and \(\alpha \beta\) into our expression: \[ \frac{\alpha}{\beta} + \frac{\beta}{\alpha} = \frac{\alpha^2 + \beta^2}{\alpha \beta} = \frac{\frac{25}{36}}{-\frac{1}{3}} \] Calculating this gives: \[ = \frac{25}{36} \times -3 = -\frac{25 \times 3}{36} = -\frac{75}{36} = -\frac{25}{12} \] ### Final Answer Thus, the value of \(\frac{\alpha}{\beta} + \frac{\beta}{\alpha}\) is: \[ \boxed{-\frac{25}{12}} \]
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ARIHANT SSC-THEORY OF EQUATIONS-INTRODUCTORY EXERCISE - 14.1
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  6. Find the quadratic equation whose roots are sqrt3 and 2sqrt3 :

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  7. If alpha and beta are the roots of equation 6x^(2)+x-2=0, find the val...

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  12. If alpha, beta be the roots of the quadratic equation 3x^(2)-6x+4=0, f...

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  13. If alpha, beta be the roots of the quadratic equation x^(2)-5x+k=0, fi...

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