If $p$ and $q$ are non-zero real numbers and $\alpha^3+\beta^3=-p, \alpha \beta=q$, then a quadratic…

If $p$ and $q$ are non-zero real numbers and $\alpha^3+\beta^3=-p, \alpha \beta=q$, then a quadratic equation whose roots are $\frac{\alpha^2}{\beta}, \frac{\beta^2}{\alpha}$ is :
  1. $p x^2-q x+p^2=0$
  2. $q x^2+p x+q^2=0$
  3. $p x^2+q x+p^2=0$
  4. $q x^2-p x+q^2=0$

Solution

Given $\alpha^3+\beta^3=-p$ and $\alpha \beta=q$ Let $\frac{\alpha^2}{\beta}$ and $\frac{\beta^2}{\alpha}$ be the root of required quadratic equation. So, $\frac{\alpha^2}{\beta}+\frac{\beta^2}{\alpha}=\frac{\alpha^3+\beta^3}{\alpha \beta}=\frac{-p}{q}$ and $\frac{\alpha^2}{\beta} \times \frac{\beta^2}{\alpha}=\alpha \beta=q$ Hence, required quadratic equation is $ \begin{aligned} &x^2-\left(\frac{-p}{q}\right) x+q=0 \\ &\Rightarrow x^2+\frac{p}{q} x+q=0 \Rightarrow q x^2+p x+q^2=0 \end{aligned} $

Asked in: JEE Main 2013 (25 Apr Online)

Practice more Quadratic Equation questions on Aicharya