Question
If one root of the quadratic equation \( 6 x^{2}-k x+48=0 \) is the square of the other, find the two roots and hence fing the value of \( k \).
Ask by Rose Guerrero. in Nigeria
Jan 19,2025
Real Tutor Solution
Tutor-Verified Answer
Answer
The roots are 2 and 4, and \( k = 36 \).
Solution
Let’s solve the quadratic equation:
\[ 6x^2 - kx + 48 = 0 \]
**Given:** One root is the square of the other. Let’s denote the roots as \( \alpha \) and \( \alpha^2 \).
For a quadratic equation \( ax^2 + bx + c = 0 \):
- **Sum of roots:** \( \alpha + \alpha^2 = \frac{k}{6} \)
- **Product of roots:** \( \alpha \cdot \alpha^2 = \frac{48}{6} = 8 \)
From the product:
\[ \alpha^3 = 8 \implies \alpha = 2 \]
(We consider only the real solution here, as complex roots would not satisfy the real coefficients of the quadratic equation.)
Now, the other root is:
\[ \alpha^2 = 2^2 = 4 \]
**Thus, the roots are 2 and 4.**
To find \( k \), use the sum of the roots:
\[ 2 + 4 = \frac{k}{6} \implies 6 = \frac{k}{6} \implies k = 36 \]
**Final Answer:**
The equation has roots 2 and 4, and the value of \( k \) is 36.
Reviewed and approved by the UpStudy tutoring team
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Mind Expander
Let the roots be \( r \) and \( r^2 \). According to Vieta's formulas, the sum of the roots \( r + r^2 \) is equal to \( \frac{k}{6} \), and the product of the roots \( r \cdot r^2 \) is equal to \( \frac{48}{6} = 8 \). From the product, we have: \[ r^3 = 8 \] Thus, \( r = 2 \). Now, substitute \( r = 2 \) into the sum equation: \[ 2 + 2^2 = 2 + 4 = 6 = \frac{k}{6} \] Multiplying both sides by 6 gives: \[ k = 36 \] The roots are \( 2 \) and \( 4 \) (since \( r^2 = 2^2 = 4 \)). So, the roots are \( 2 \) and \( 4 \) and \( k = 36 \)!