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If both roots of the equation x^(2)-(m-3...

If both roots of the equation `x^(2)-(m-3)x+m=0(m epsilonR)` are positive, then

A

`m epsilon (3,oo)`

B

`m epsilon(-oo,1]`

C

`m epsilon[9,oo)`

D

`m epsilon(1,3)`

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The correct Answer is:
To solve the problem, we need to analyze the quadratic equation given by: \[ x^2 - (m - 3)x + m = 0 \] We want to find the conditions under which both roots of this equation are positive. ### Step 1: Determine the Discriminant For the roots to be real, the discriminant (D) must be non-negative. The discriminant for a quadratic equation \( ax^2 + bx + c = 0 \) is given by: \[ D = b^2 - 4ac \] Here, \( a = 1 \), \( b = -(m - 3) \), and \( c = m \). Thus, we have: \[ D = (m - 3)^2 - 4(1)(m) \] ### Step 2: Set Up the Inequality We need to ensure that the discriminant is non-negative: \[ (m - 3)^2 - 4m \geq 0 \] Expanding this gives: \[ m^2 - 6m + 9 - 4m \geq 0 \] This simplifies to: \[ m^2 - 10m + 9 \geq 0 \] ### Step 3: Factor the Quadratic Next, we factor the quadratic: \[ m^2 - 10m + 9 = (m - 1)(m - 9) \] Thus, we need to solve the inequality: \[ (m - 1)(m - 9) \geq 0 \] ### Step 4: Analyze the Inequality To find the intervals where this inequality holds, we can use a number line. The critical points are \( m = 1 \) and \( m = 9 \). - For \( m < 1 \): Both factors are negative, so the product is positive. - For \( 1 < m < 9 \): One factor is positive and the other is negative, so the product is negative. - For \( m > 9 \): Both factors are positive, so the product is positive. Thus, the solution to the inequality is: \[ m \in (-\infty, 1] \cup [9, \infty) \] ### Step 5: Ensure Both Roots are Positive Next, we need to ensure that both roots are positive. The sum and product of the roots can help us here. 1. **Sum of the Roots**: The sum of the roots is given by: \[ S = -\frac{b}{a} = m - 3 \] For both roots to be positive, we need: \[ m - 3 > 0 \Rightarrow m > 3 \] 2. **Product of the Roots**: The product of the roots is given by: \[ P = \frac{c}{a} = m \] For both roots to be positive, we also need: \[ m > 0 \] ### Step 6: Combine Conditions We now combine the conditions we found: 1. From the discriminant, we have \( m \in (-\infty, 1] \cup [9, \infty) \). 2. From the sum of roots, we have \( m > 3 \). 3. From the product of roots, we have \( m > 0 \). The only interval that satisfies all these conditions is: \[ m \in [9, \infty) \] ### Final Answer Thus, the values of \( m \) for which both roots of the equation are positive is: \[ m \in [9, \infty) \]
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