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If the roots of ax^(2) + bx + c = 0 (a g...

If the roots of `ax^(2) + bx + c = 0 (a gt 0)` be each greater than unity, then

A

a + b + c = 0

B

a + b + c `gt` 0

C

a + b + c `lt` 0

D

none of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to establish the conditions under which both roots of the quadratic equation \( ax^2 + bx + c = 0 \) (where \( a > 0 \)) are greater than unity. ### Step-by-Step Solution: 1. **Understanding the Roots**: Let the roots of the quadratic equation be \( \alpha \) and \( \beta \). According to the problem, both roots are greater than 1, i.e., \( \alpha > 1 \) and \( \beta > 1 \). 2. **Using Vieta's Formulas**: From Vieta's formulas, we know: - The sum of the roots \( \alpha + \beta = -\frac{b}{a} \) - The product of the roots \( \alpha \beta = \frac{c}{a} \) 3. **Condition for Roots Greater than 1**: Since both roots are greater than 1, we can derive the following conditions: - For the sum of the roots: \[ \alpha + \beta > 2 \implies -\frac{b}{a} > 2 \implies b < -2a \] - For the product of the roots: \[ \alpha \beta > 1 \implies \frac{c}{a} > 1 \implies c > a \] 4. **Evaluating the Function at \( x = 1 \)**: To ensure that the quadratic does not cross the x-axis between the roots (since both roots are greater than 1), we evaluate the quadratic function at \( x = 1 \): \[ f(1) = a(1)^2 + b(1) + c = a + b + c \] Since both roots are greater than 1, we need \( f(1) > 0 \): \[ a + b + c > 0 \] 5. **Summary of Conditions**: Therefore, the conditions for the quadratic equation \( ax^2 + bx + c = 0 \) to have both roots greater than 1 are: - \( b < -2a \) - \( c > a \) - \( a + b + c > 0 \) ### Conclusion: The conditions that must be satisfied for the roots of the quadratic equation \( ax^2 + bx + c = 0 \) to be each greater than unity are: 1. \( b < -2a \) 2. \( c > a \) 3. \( a + b + c > 0 \)

To solve the problem, we need to establish the conditions under which both roots of the quadratic equation \( ax^2 + bx + c = 0 \) (where \( a > 0 \)) are greater than unity. ### Step-by-Step Solution: 1. **Understanding the Roots**: Let the roots of the quadratic equation be \( \alpha \) and \( \beta \). According to the problem, both roots are greater than 1, i.e., \( \alpha > 1 \) and \( \beta > 1 \). 2. **Using Vieta's Formulas**: ...
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