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If x^(2) - px + 4 gt 0 for all real va...

If ` x^(2) - px + 4 gt 0 ` for all real value of x,then which one of the following is correct ?

A

`|p| lt 4`

B

`|p| le 4`

C

` |p| gt4`

D

`|p| ge 4`

Text Solution

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The correct Answer is:
To solve the problem, we need to determine the conditions under which the quadratic expression \( x^2 - px + 4 \) is greater than zero for all real values of \( x \). ### Step-by-step Solution: 1. **Identify the Quadratic Expression**: The given expression is \( x^2 - px + 4 \). 2. **Condition for Positivity**: A quadratic expression \( ax^2 + bx + c \) is positive for all real \( x \) if its discriminant is less than zero. The discriminant \( D \) is given by the formula: \[ D = b^2 - 4ac \] Here, \( a = 1 \), \( b = -p \), and \( c = 4 \). 3. **Calculate the Discriminant**: Substitute the values of \( a \), \( b \), and \( c \) into the discriminant formula: \[ D = (-p)^2 - 4 \cdot 1 \cdot 4 \] Simplifying this gives: \[ D = p^2 - 16 \] 4. **Set the Discriminant Less Than Zero**: For the quadratic to be positive for all \( x \), we need: \[ p^2 - 16 < 0 \] 5. **Solve the Inequality**: Rearranging the inequality: \[ p^2 < 16 \] Taking the square root of both sides gives: \[ |p| < 4 \] This implies: \[ -4 < p < 4 \] 6. **Conclusion**: The condition for \( p \) is that \( p \) must lie within the interval \( (-4, 4) \). ### Final Answer: Thus, the correct option is that \( p \) must be in the range \( -4 < p < 4 \).

To solve the problem, we need to determine the conditions under which the quadratic expression \( x^2 - px + 4 \) is greater than zero for all real values of \( x \). ### Step-by-step Solution: 1. **Identify the Quadratic Expression**: The given expression is \( x^2 - px + 4 \). 2. **Condition for Positivity**: ...
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NDA PREVIOUS YEARS-POLYNOMIAL,QUADRATIC EQUATION & INEQUALITIES-Math
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