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1.3 The roots of a quadratic equation are \( x=\frac{-10 \pm \sqrt{100-4 k^{2}}}{2 k} \). Calculate the values of \( k \) for which the roots are: 1.3.1 equal 1.3 .2 non-real

Ask by Harris Cervantes. in South Africa
Feb 18,2025

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The roots are equal when \( k = 5 \) or \( k = -5 \). The roots are non-real when \( |k| > 5 \) (i.e., \( k < -5 \) or \( k > 5 \)).

Solution

We are given the roots of a quadratic equation in the form   x = (–10 ± √(100 – 4k²)) / (2k). This expression is based on the quadratic formula for an equation of the type   kx² + 10x + k = 0      (with k ≠ 0). To decide when the roots are equal or non-real, we need to examine the discriminant, which in this formula is the expression under the square root. Step 1. Find the Discriminant The discriminant, Δ, is given by   Δ = 100 – 4k². Step 2. Conditions for the Types of Roots 1. Equal Roots: The roots are equal when Δ = 0.   100 – 4k² = 0   => 4k² = 100   => k² = 25   => k = 5 or k = –5. So, the roots are equal when k = 5 or k = –5. 2. Non-real (Complex) Roots: The roots are non-real when Δ < 0.   100 – 4k² < 0   => 4k² > 100   => k² > 25   => |k| > 5   => k < –5 or k > 5. Thus, the roots are non-real when |k| > 5 (that is, when k < –5 or k > 5). Note: We exclude k = 0 because the quadratic formula given would be undefined (division by zero), and the original quadratic equation would no longer be quadratic. Final Answers: 1.3.1 Equal roots occur when k = 5 or k = –5. 1.3.2 Non-real roots occur when |k| > 5 (i.e., k < –5 or k > 5).

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For the roots of a quadratic equation to be equal, the discriminant must be zero. Here, the discriminant is given by \( 100 - 4k^2 \). Setting this equal to zero gives us \( 100 - 4k^2 = 0 \), which simplifies to \( 4k^2 = 100 \) and further \( k^2 = 25 \). Thus, the values of \( k \) that make the roots equal are \( k = 5 \) or \( k = -5 \). For the roots to be non-real, the discriminant must be less than zero. That means we need \( 100 - 4k^2 < 0 \). Rearranging gives us \( 4k^2 > 100 \), which simplifies to \( k^2 > 25 \). Therefore, \( k > 5 \) or \( k < -5 \) will yield non-real roots.

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