NDA 2024
- Exam
- NDA
- Year
- 2024
- Subject
- Mathematics
- Chapter
- Quadratic Equation
NDA 2024 · Mathematics · Quadratic Equation
If a, b and c(a 0, c 0) are in GP, then consider the following in...
If a, b and are in GP, then consider the following in respect of the equation
1. The equation has imaginary roots.
2. The ratio of the roots of the equation is where is a cube root of unity.
3. The product of roots of the equation is .
Which of the statements given above are correct?
Options
- A1 and 2 only
- B2 and 3 only
- C1 and 3 only
- D1,2 and 3
Correct answer
D. 1,2 and 3
Step-by-step solution
Given that are in GP
Now, 1. $\therefore$ Roots are imaginary (correct)
Let, $\quad a=2, b=4, c=8\begin{aligned}
\therefore \quad x^2+2 x+4 & =0 \\
\Rightarrow \quad x & =\frac{-2 \pm \sqrt{4-16}}{2}=-1 \pm \sqrt{3}
\end{aligned}$
2. Ratio of roots $=\frac{-1+\sqrt{3}}{-1-\sqrt{3}}=\frac{\omega}{\omega^2}=\frac{1}{\omega}$ (correct)
3.\begin{aligned}
\text{ Product of roots } & =\frac{(-1+\sqrt{3})(-1-\sqrt{3})}{2} \times 4 \\
& =\omega \cdot \omega^2 \cdot 4=4=\frac{b^2}{a^2}
\end{aligned}$$ (correct)
Hence, statements 1,2 and 3 are correct.