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If a,b,c in R and a+b+c=0, then the quad...

If `a,b,c in R and a+b+c=0`, then the quadratic equation `4ax^(2)+3bx +2c=0` has

A

one positive and one negative root

B

imaginary roots

C

real roots

D

none of these

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The correct Answer is:
To solve the problem, we need to analyze the quadratic equation given by \(4ax^2 + 3bx + 2c = 0\) under the condition \(a + b + c = 0\). ### Step-by-step Solution: 1. **Identify the coefficients**: - The coefficients of the quadratic equation are: - \(A = 4a\) - \(B = 3b\) - \(C = 2c\) 2. **Calculate the discriminant**: - The discriminant \(D\) of a quadratic equation \(Ax^2 + Bx + C = 0\) is given by: \[ D = B^2 - 4AC \] - Substituting the values of \(A\), \(B\), and \(C\): \[ D = (3b)^2 - 4(4a)(2c) = 9b^2 - 32ac \] 3. **Substitute \(b\)**: - From the condition \(a + b + c = 0\), we can express \(b\) in terms of \(a\) and \(c\): \[ b = -a - c \] - Substitute this into the discriminant: \[ D = 9(-a - c)^2 - 32ac \] 4. **Expand the expression**: - Expanding \(D\): \[ D = 9(a^2 + 2ac + c^2) - 32ac \] \[ D = 9a^2 + 18ac + 9c^2 - 32ac \] \[ D = 9a^2 - 14ac + 9c^2 \] 5. **Analyze the discriminant**: - The discriminant \(D = 9a^2 - 14ac + 9c^2\) can be rewritten as: \[ D = 9(a^2 + c^2) - 14ac \] - This expression is a quadratic in terms of \(a\) and \(c\). 6. **Determine the nature of the roots**: - The expression \(D\) is a quadratic function in \(a\) and \(c\). Since \(9(a^2 + c^2)\) is always non-negative and \(14ac\) is a product of two real numbers, we can conclude: - The discriminant \(D\) can be zero or positive, depending on the values of \(a\) and \(c\). - If \(D > 0\), the roots are real and distinct. - If \(D = 0\), the roots are real and equal. ### Conclusion: Given that \(D\) can be zero or positive, we conclude that the quadratic equation \(4ax^2 + 3bx + 2c = 0\) has real roots.
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