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The number of negative intergral values ...

The number of negative intergral values of m for which the expression `x ^(2) + 2(m -1) x +m +5` is positive `AA x gt 1` is:

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To solve the problem, we need to determine the number of negative integral values of \( m \) for which the expression \( x^2 + 2(m - 1)x + (m + 5) \) is positive for all \( x > 1 \). ### Step-by-Step Solution: 1. **Identify the Quadratic Expression**: The given expression is: \[ f(x) = x^2 + 2(m - 1)x + (m + 5) \] This is a quadratic function in \( x \). 2. **Condition for the Quadratic to be Positive**: For the quadratic to be positive for all \( x > 1 \), the coefficient of \( x^2 \) must be positive (which it is, as it equals 1), and the discriminant must be negative. 3. **Calculate the Discriminant**: The discriminant \( D \) of a quadratic \( ax^2 + bx + c \) is given by: \[ D = b^2 - 4ac \] Here, \( a = 1 \), \( b = 2(m - 1) \), and \( c = m + 5 \). Therefore, we have: \[ D = [2(m - 1)]^2 - 4 \cdot 1 \cdot (m + 5) \] Simplifying this: \[ D = 4(m - 1)^2 - 4(m + 5) \] \[ D = 4[(m - 1)^2 - (m + 5)] \] 4. **Set the Discriminant Less Than Zero**: We need: \[ (m - 1)^2 - (m + 5) < 0 \] Expanding this: \[ (m^2 - 2m + 1) - m - 5 < 0 \] \[ m^2 - 3m - 4 < 0 \] 5. **Factor the Quadratic**: We can factor \( m^2 - 3m - 4 \): \[ (m + 1)(m - 4) < 0 \] 6. **Determine the Intervals**: The roots of the equation are \( m = -1 \) and \( m = 4 \). The quadratic will be negative between the roots: \[ -1 < m < 4 \] 7. **Identify the Integral Values of \( m \)**: The integral values of \( m \) in the interval \( (-1, 4) \) are: \[ 0, 1, 2, 3 \] These are all the integral values of \( m \) that satisfy the condition. 8. **Count the Negative Integral Values**: The negative integral values of \( m \) in the interval \( (-1, 4) \) are none. Thus, the number of negative integral values of \( m \) is: \[ \text{Number of negative integral values of } m = 0 \] ### Final Answer: The number of negative integral values of \( m \) for which the expression is positive for all \( x > 1 \) is \( 0 \).
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VIKAS GUPTA (BLACK BOOK) ENGLISH-QUADRATIC EQUATIONS -EXERCISE (SUBJECTIVE TYPE PROBLEMS)
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