Location of Roots in Quadratic Equation. We learnt about the location of roots of quadratic equation in class today. I have a problem in one case specifically, the one where both the roots are required in the interval (k_1, k_2) where k_1, k_2 are real constant numbers.

Aliyah Thompson

Aliyah Thompson

Answered question

2022-11-14

Location of Roots in Quadratic Equation
We learnt about the location of roots of quadratic equation in class today. I have a problem in one case specifically, the one where both the roots are required in the interval ( k 1 , k 2 ) where k 1 , k 2 are real constant numbers. So the conditions given to us were,
1. Δ greater than or equal to 0 (fairly obvious)
2. a f ( k 1 ) > 0 where f ( k 1 ) is the value of the function at k 1 and a is the leading coefficient
3. a f ( k 2 ) > 0 (both of these are again understandable)
4. then comes k 1 < b / 2 a < k 2 i.e. the abscissa of the vertex of the parabola lies in the interval required.

Answer & Explanation

gortepap6yb

gortepap6yb

Beginner2022-11-15Added 19 answers

Explanation:
You're missing an essential point: conditions 2 and 3 mean that k 1 and k 2 are outside the interval of the roots. However, they might be on the same side of this interval.
Step 2
Therefore, supposing conditions 2 and 3 is not enough, we must add the condition that k 1 , k 2 are not on the same side, which is equivalent to their arithmetic mean being in the interval ( k 1 , k 2 ).

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