Question:
If $\alpha$ and $\beta$ are the roots of the equation, $7 x^{2}-3 x-2=0$,
the the value of $\frac{\alpha}{1-\alpha^{2}}+\frac{\beta}{1-\beta^{2}}$ is equal to :
Correct Option: , 4
Solution:
Let $\alpha$ and $\beta$ be the roots of the quadratic equation
$7 x^{2}-3 x-2=0$
$\therefore \alpha+\beta=\frac{3}{7}, \alpha \beta=\frac{-2}{7}$
Now, $\frac{\alpha}{1-\alpha^{2}}+\frac{\beta}{1-\beta^{2}}$
$=\frac{\alpha-\alpha \beta(\alpha+\beta)+\beta}{1-\left(\alpha^{2}+\beta^{2}\right)+(\alpha \beta)^{2}}$
$=\frac{(\alpha+\beta)-\alpha \beta(\alpha+\beta)}{1-(\alpha+\beta)^{2}+2 \alpha \beta+(\alpha \beta)^{2}}$
$=\frac{\frac{3}{7}+\frac{2}{7} \times \frac{3}{7}}{1-\frac{9}{49}+2 \times \frac{-2}{7}+\frac{4}{49}}=\frac{27}{16}$