JEE MATHEMATICS MCQ: QUADRATIC EQUATIONS

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Analyzing +4 | -1

If the function

f\left( x \right) = {x^3} + 3\left( {a - 7} \right){x^2} + 3\left( {{a^2} - 9} \right)x - 1

has positive points of extremum then

View answer and explanation

Correct option: B

a \in \left( { - \infty ,\; - 3} \right) \cup \left( {3,\;29/7} \right)

Option B (

a \in \left( { - \infty ,\; - 3} \right) \cup \left( {3,\;29/7} \right)

) is correct because it satisfies the conditions for the function to have positive points of extremum.

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{x^2} + 4ax + 2 > 0

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