JEE MainMathematicsQuadratic Equation and InequalitiesMCQ+4 / −1
The integer 'k', for which the inequality x2 2(3k 1)x + 8k2 7 > 0 is valid for every x in R, is :
- A4
- B2
- C3
- D0
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Correct answer: C
- We are given the quadratic inequality
which must be valid for every .
- For a quadratic
the necessary and sufficient conditions are:
- discriminant
Here,
so we only need:
- Identify coefficients:
Thus,
- Simplify:
So,
Now,
Hence,
- For positivity for all real :
This holds when
- Since is an integer, the only possible value is
- Check options:
- A: → gives , not strictly positive for all
- B: → gives , not strictly positive for all
- C: → valid
- D: → gives , not valid
Therefore, the correct option is:
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