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If the height that a toy airplane can fly is given by the following expression: \( -3 x^{2}-5 x+9 \). Determine the maximum height that the airplane can fly.

Ask by Mathis Deleon. in South Africa
Feb 25,2025

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Answer

The maximum height the toy airplane can fly is 133/12 units, which is approximately 11.08 units.

Solution

We are given the height function:   h(x) = –3x² – 5x + 9 Since this is a quadratic function with a negative coefficient for x² (a = –3), its graph is a downward-opening parabola. Therefore, it has a maximum value at its vertex. Step 1. Find the x-coordinate of the vertex using the formula:   x = –b / (2a) Here, a = –3 and b = –5, so:   x = –(–5) / [2(–3)] = 5 / (–6) = –5/6 Step 2. Find the maximum height by substituting x = –5/6 back into the height function:   h(–5/6) = –3(–5/6)² – 5(–5/6) + 9 First calculate (–5/6)²:   (–5/6)² = 25/36 Now substitute:   h(–5/6) = –3 × (25/36) + (25/6) + 9 Simplify each term:   –3 × (25/36) = –75/36   Convert (25/6) to a fraction with denominator 36: 25/6 = 150/36   Convert 9 = 324/36 Now, combine the terms:   h(–5/6) = (–75 + 150 + 324) / 36 = 399/36 Simplify 399/36 by dividing numerator and denominator by 3:   399 ÷ 3 = 133  and 36 ÷ 3 = 12 Thus,   h(–5/6) = 133/12 Step 3. Write the conclusion: The maximum height that the toy airplane can fly is 133/12. If you prefer a decimal approximation, 133/12 ≈ 11.08. So, the maximum height is 133/12 units.

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Mind Expander

To find the maximum height of the toy airplane represented by the quadratic equation \( -3x^{2}-5x+9 \), we can use the vertex formula, which gives the x-coordinate of the vertex as \( x = -\frac{b}{2a} \). Here, \( a = -3 \) and \( b = -5 \). Calculating gives us: \[ x = -\frac{-5}{2 \times -3} = \frac{5}{-6} = -\frac{5}{6}. \] Next, we substitute this value back into the original expression to find the maximum height: \[ -\left(3\left(-\frac{5}{6}\right)^{2} + 5\left(-\frac{5}{6}\right) + 9\right). \] Calculating this results in a maximum height of \( 10.25 \). This means the toy airplane can soar to a fantastic height of \( 10.25 \) units! It's important to note that maximizing the height of a quadratic function involves understanding its parabola shape, which opens downwards when the leading coefficient (a) is negative. This dynamic behavior of quadratics can be key in various real-world scenarios, such as predicting projectile motion or optimizing design features in engineering.

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