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What is the smallest integral value oof ...

What is the smallest integral value oof k for which the roots `3x^(2)+8x-k=0` are real?

A

`-6`

B

`-5`

C

`0`

D

`6`

Text Solution

AI Generated Solution

The correct Answer is:
To determine the smallest integral value of \( k \) for which the roots of the quadratic equation \( 3x^2 + 8x - k = 0 \) are real, we need to analyze the discriminant of the quadratic equation. ### Step-by-Step Solution: 1. **Identify the coefficients**: The given quadratic equation is in the form \( ax^2 + bx + c = 0 \), where: - \( a = 3 \) - \( b = 8 \) - \( c = -k \) 2. **Write the condition for real roots**: For the roots of a quadratic equation to be real, the discriminant \( D \) must be greater than or equal to zero. The discriminant is given by: \[ D = b^2 - 4ac \] Therefore, we need: \[ D \geq 0 \] 3. **Substitute the values of \( a \), \( b \), and \( c \)**: Substituting the values into the discriminant formula, we get: \[ D = 8^2 - 4 \cdot 3 \cdot (-k) \] 4. **Calculate the discriminant**: \[ D = 64 + 12k \] 5. **Set up the inequality**: To ensure the roots are real, we set up the inequality: \[ 64 + 12k \geq 0 \] 6. **Solve for \( k \)**: Rearranging the inequality gives: \[ 12k \geq -64 \] Dividing both sides by 12: \[ k \geq -\frac{64}{12} \] Simplifying the fraction: \[ k \geq -\frac{16}{3} \approx -5.33 \] 7. **Determine the smallest integral value of \( k \)**: Since \( k \) must be an integer, the smallest integer greater than or equal to \(-5.33\) is: \[ k = -5 \] ### Conclusion: The smallest integral value of \( k \) for which the roots of the equation \( 3x^2 + 8x - k = 0 \) are real is: \[ \boxed{-5} \]
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