INSTRUCTION: From the words lettered A-D choose the appropriate answer
If \(\alpha\) and \(\beta\) are the roots of the quadratic equation \(x^2-10 x+2=0\). Find the value of \(\frac{1}{a^2}+\frac{1}{\beta^2}\)
A. 26 B. 24 C. \(3 / 2\) D. 3
Correct Answer: B
Explanation
To find the value of \(\frac{1}{\alpha^2}+\frac{1}{\beta^2}\) Take the L.C.M \(\Rightarrow \frac{\beta^2+\alpha^2}{\alpha^2 \beta^2}=\frac{\beta^2+a^2}{(\alpha \beta)^2}\) Where \(\alpha^2+\beta^2 \equiv(\alpha+\beta)^2-2 \alpha \beta\) Since \(\alpha\) and \(\beta\) are the roots of the equation \begin{array}{l} x^2-10 x+2=0 \\ a=1, b=-10, c=2 \end{array} then sum of the roots \begin{array}{l} \alpha+\beta=-\frac{b}{a} \\ \alpha+\beta=-\frac{(-10)}{1}=10 \\ \alpha \beta=\frac{c}{a}=\frac{2}{1}=2 \end{array} thus \begin{aligned} \frac{\alpha^2+\beta^2}{(\alpha \beta)^2} &=\frac{(\alpha+\beta)^2-2 \alpha \beta}{(\alpha \beta)^2} \\ &=\frac{10^2-2(2)}{(2)^2} \\ &=\frac{100-4}{4}=\frac{96}{4}=24 \end{aligned}