Question:
If the sum of two roots of the cubic equation $x^3 - 5x^2 - 2x + 24 = 0$ is $2$, then the roots of the equation are:
If the sum of two roots of the cubic equation $x^3 - 5x^2 - 2x + 24 = 0$ is $2$, then the roots of the equation are:
Show Hint
Use options to save time! Only option (A) contains the roots $-2, 3, 4$, which sum up to $5$ and have a pairwise product sum of $-2(3) + 3(4) + 4(-2) = -6 + 12 - 8 = -2$.
Updated On: Jun 3, 2026
- $-2, 3, 4$
- $2, 3, 0$
- $-1, 3, 3$
- $-2, -3, -4$
Show Solution
Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Concept
Let the roots of the cubic equation be $\alpha, \beta, \gamma$. According to Vieta's formulas: \[ \alpha + \beta + \gamma = -\frac{b}{a} \] \[ \alpha\beta\gamma = -\frac{d}{a} \]
Step 2: Meaning
We are given the sum of two roots, say $\alpha + \beta = 2$. We can find the third root $\gamma$ directly from the sum formula.
Step 3: Analysis
From the given cubic equation $x^3 - 5x^2 - 2x + 24 = 0$, we have: \[ \alpha + \beta + \gamma = 5 \] Since $\alpha + \beta = 2$: \[ 2 + \gamma = 5 \implies \gamma = 3 \] Thus, $3$ is one of the roots. Now, use the product of the roots formula: \[ \alpha\beta\gamma = -24 \implies \alpha\beta(3) = -24 \implies \alpha\beta = -8 \] We also have $\alpha + \beta = 2$. Solving these quadratic relations: \[ t^2 - 2t - 8 = 0 \implies (t - 4)(t + 2) = 0 \implies t = 4 \text{ or } t = -2 \] Hence, the roots are $-2, 3, 4$.
Step 4: Conclusion
The roots of the cubic equation are $-2, 3, 4$.
Final Answer: (A)
Let the roots of the cubic equation be $\alpha, \beta, \gamma$. According to Vieta's formulas: \[ \alpha + \beta + \gamma = -\frac{b}{a} \] \[ \alpha\beta\gamma = -\frac{d}{a} \]
Step 2: Meaning
We are given the sum of two roots, say $\alpha + \beta = 2$. We can find the third root $\gamma$ directly from the sum formula.
Step 3: Analysis
From the given cubic equation $x^3 - 5x^2 - 2x + 24 = 0$, we have: \[ \alpha + \beta + \gamma = 5 \] Since $\alpha + \beta = 2$: \[ 2 + \gamma = 5 \implies \gamma = 3 \] Thus, $3$ is one of the roots. Now, use the product of the roots formula: \[ \alpha\beta\gamma = -24 \implies \alpha\beta(3) = -24 \implies \alpha\beta = -8 \] We also have $\alpha + \beta = 2$. Solving these quadratic relations: \[ t^2 - 2t - 8 = 0 \implies (t - 4)(t + 2) = 0 \implies t = 4 \text{ or } t = -2 \] Hence, the roots are $-2, 3, 4$.
Step 4: Conclusion
The roots of the cubic equation are $-2, 3, 4$.
Final Answer: (A)
Was this answer helpful?
0
0
Top AP EAPCET Mathematics Questions
- $D = \left\{x\in\mathbb{R}: f\left(x\right) =\sqrt{\frac{x - \left|x\right|}{x - \left[x\right]}} \text{is defined} \right\}$ and $C$ be the range of the real function $g(x) = \frac{2x}{4 + x^{2}}$. Then $D \cap C$
- $f\left(x\right) = \frac{x}{e^{x}-1} + \frac{x}{2} + 2 \cos^{3} \frac{x}{2} $ on $R-\left\{0\right\} $ is
- Consider the following lists.
List-I List-II (A) $f(x) = \frac{|x+2|}{x+2} , x \ne -2 $ (I) $[\frac{1}{3} , 1 ]$ (B) $(x)=|[x]|,x \in [R$ (II) Z (C) $h(x) = |x - [x]| , x \in [R$ (III) W (D) $f(x) = \frac{1}{2 - \sin 3x} , x \in [R$ (IV) [0, 1) (V) { -1, 1} - If $[x]$ is the greatest integer less than or equal to $x$ and $|x|$ is the modulus of $x$. then the system of three equations $2x + 3 | y | + 5[z] = 0, x + |y| - 2[z] = 4, x + |y| + |z| = 1$ has
- Investigate the values of $\lambda$ and $\mu$ for the system $x+2 y+3 z=6, x+3 y+5 z=9$, $2 x+5 y+\lambda z=\mu$ and match the values in List - I with the items in List - II.
List I List II (A) $\lambda=8, \mu \neq 15$ 1. Infinitely many solutions (B) $\lambda \neq 8, \mu \in R$ 2. No solution (C) $\lambda=8, \mu=15$ 3. Unique solution
View More Questions
Top AP EAPCET Algebra Questions
- If \( \alpha \) and \( \beta \) are the roots of the equation \( 2x^2 - 4x + 3 = 0 \), then \( \frac{2(\alpha^4 + \beta^4) + 3(\alpha^2 + \beta^2)}{\alpha + \beta} = \)
- If \( \alpha \) and \( \beta \) are the roots of the equation \( ax^2 + bx + c = 0 \), then the equation whose roots are \( \alpha + \beta \) and \( \frac{1}{\alpha} + \frac{1}{\beta} \) is
- If the roots of the equation \( 16x^3 - 44x^2 + 36x - 9 = 0 \) are in harmonic progression, then its greatest root is
- If \( \frac{x^4 - 6x^3 + 9x^2 + 5x - 20}{x^2 - x - 2} = f(x) + \frac{a}{x + p} + \frac{b}{x + q} \), then \( 2(a + b) = \)
- The number of solutions of the equations \[ x + y + z = 1,\quad x^2 + y^2 + z^2 = 1,\quad x^3 + y^3 + z^3 = 1 \] is:
View More Questions
Top AP EAPCET Questions
- A body is projected from the ground at an angle of $\tan^{-1} \left( \frac{8}{7}\right)$ with the horizontal. The ratio of the maximum height attained by it to its range is
- The four quantum numbers of the valence electron of potassium are :
- A lens forms real and virtual images of an object, when the object is at $u_{1}$ and $u_{2}$ distances respectively. If the size of the virtual image is double that of the real image, then the focal length of the lens is (take, the magnification of the real image as $m$ )
- Two spheres $P$ and $Q$, each of mass $200\, g$ are attached to a string of length one metre as shown in the figure. The string and the spheres are then whirled in a horizontal circle about $O$ at a constant angular speed. The ratio of the tension in the string between $P$ and $Q$ to that of between $P$ and $O$ is $(P$ is at mid-point of the line joining $O$ and $Q$ )
- The volume of $0.02\, M$ acidified permanganate solution required for complete reaction of $60\, mL$ of $0.01\, MI^{-}$ ion solution to form $I_2$ in $mL$ is
View More Questions