Let $\alpha$, $\beta$, $\gamma$ be the real roots of the equation, x3 + ax2 + bx + c = 0, (a, b, c $\in$ R and a, b $\ne$ 0). If the system of equations (in u, v, w) given by $\alpha$u + $\beta$v + $\gamma$w = 0, $\beta$u + $\gamma$v + $\alpha$w = 0; $\gamma$u + $\alpha$v + $\beta$w = 0 has non-trivial solution, then the value of ${{{a^2}} \over b}$ is
Solution
x<sup>3</sup> + ax<sup>2</sup> + bx + c = 0 <br><br>Roots are $\alpha$, $\beta$, $\gamma$.<br><br>For non-trivial solutions,<br><br>$$\left| {\matrix{
\alpha & \beta & \gamma \cr
\beta & \gamma & \alpha \cr
\gamma & \alpha & \beta \cr
} } \right| = 0$$<br><br>$\Rightarrow$ ${\alpha ^3} + {\beta ^3} + {\gamma ^3} - 3\alpha \beta \gamma = 0$<br><br>$\Rightarrow$ $$(\alpha + \beta + \gamma )\left[ {{{\left( {\alpha + \beta + \alpha } \right)}^2} - 3\left( {\sum {\alpha \beta } } \right)} \right] = 0$$<br><br>$\Rightarrow$ $( - a)[{a^2} - 3b] = 0$<br><br>$\Rightarrow$ ${a^2} = 3b$ ($\because$ a $\ne$ 0)<br><br>$\Rightarrow {{{a^2}} \over b} = 3$
About this question
Subject: Mathematics · Chapter: Matrices and Determinants · Topic: Types of Matrices and Operations
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