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If x^(2)+bx+x=0 has no real roots and a+...

If `x^(2)+bx+x=0` has no real roots and `a+b+c lt 0` then

A

`4a+2b+x gt 0`

B

`a-b+c=0`

C

`c lt 0`

D

`a+b+c=0`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the quadratic equation given by \( x^2 + bx + c = 0 \) under the conditions that it has no real roots and \( a + b + c < 0 \). ### Step-by-Step Solution: 1. **Identify the Condition for No Real Roots**: A quadratic equation \( ax^2 + bx + c = 0 \) has no real roots if its discriminant \( D < 0 \). The discriminant \( D \) for the equation \( x^2 + bx + c = 0 \) is given by: \[ D = b^2 - 4ac \] Since \( a = 1 \) in our case, the discriminant simplifies to: \[ D = b^2 - 4c \] Therefore, for the equation to have no real roots, we must have: \[ b^2 - 4c < 0 \] This implies: \[ b^2 < 4c \] 2. **Using the Condition \( a + b + c < 0 \)**: Given \( a + b + c < 0 \) and substituting \( a = 1 \), we have: \[ 1 + b + c < 0 \] Rearranging this gives: \[ b + c < -1 \] 3. **Combining the Conditions**: We now have two inequalities: - \( b^2 < 4c \) - \( b + c < -1 \) From the second inequality, we can express \( c \) in terms of \( b \): \[ c < -1 - b \] Substituting this into the first inequality: \[ b^2 < 4(-1 - b) \] Simplifying this gives: \[ b^2 < -4 - 4b \] Rearranging leads to: \[ b^2 + 4b + 4 < 0 \] This can be factored as: \[ (b + 2)^2 < 0 \] 4. **Analyzing the Result**: The expression \( (b + 2)^2 < 0 \) is never true for real numbers since a square of a real number is always non-negative. Therefore, the only way for the original conditions to hold is if the quadratic has no real roots and \( a + b + c < 0 \) is satisfied. 5. **Conclusion**: The conditions imply that \( b + 2 = 0 \) or \( b = -2 \) is the only case where the quadratic can be at the boundary of having no real roots, and hence \( c \) must be less than \( -1 \). ### Final Answer: Thus, the conditions lead us to conclude that \( c < -1 \) and \( b = -2 \).
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