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5. \( y=-2 x^{2}+3 x-5 \)

Ask by Stewart Carrillo. in the United States
Jan 24,2025

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The quadratic function \( y = -2x^{2} + 3x - 5 \) is a downward-opening parabola with its vertex at \( \left( \frac{3}{4}, -\frac{31}{8} \right) \). It has no real x-intercepts and its y-intercept is at \( (0, -5) \).

Solution

Certainly! Let's analyze the quadratic function provided: \[ y = -2x^{2} + 3x - 5 \] This is a quadratic equation of the form \( y = ax^{2} + bx + c \), where: - \( a = -2 \) - \( b = 3 \) - \( c = -5 \) ### 1. **Direction of the Parabola** Since \( a = -2 \) is negative, the parabola opens **downward**. ### 2. **Vertex of the Parabola** The vertex form of a quadratic equation is: \[ y = a(x - h)^2 + k \] Where \((h, k)\) is the vertex. To find the vertex, we can use the formula: \[ h = -\frac{b}{2a} \] \[ k = y(h) \] **Calculating \( h \):** \[ h = -\frac{b}{2a} = -\frac{3}{2(-2)} = -\frac{3}{-4} = \frac{3}{4} \] **Calculating \( k \):** \[ k = -2\left(\frac{3}{4}\right)^2 + 3\left(\frac{3}{4}\right) - 5 \] \[ k = -2\left(\frac{9}{16}\right) + \frac{9}{4} - 5 \] \[ k = -\frac{18}{16} + \frac{36}{16} - \frac{80}{16} \] \[ k = \left(-18 + 36 - 80\right) \div 16 \] \[ k = -62 \div 16 \] \[ k = -\frac{31}{8} \] **Vertex Coordinates:** \[ \left( \frac{3}{4}, -\frac{31}{8} \right) \] ### 3. **Axis of Symmetry** The axis of symmetry is the vertical line that passes through the vertex: \[ x = h = \frac{3}{4} \] ### 4. **Y-intercept** The y-intercept occurs where \( x = 0 \): \[ y = -2(0)^2 + 3(0) - 5 = -5 \] **Y-intercept: \( (0, -5) \)** ### 5. **X-intercepts (Roots)** To find the x-intercepts, set \( y = 0 \) and solve for \( x \): \[ 0 = -2x^{2} + 3x - 5 \] This is a quadratic equation of the form \( ax^2 + bx + c = 0 \). We can use the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] **Calculating the discriminant (\( \Delta \)):** \[ \Delta = b^2 - 4ac = 3^2 - 4(-2)(-5) = 9 - 40 = -31 \] Since the discriminant is negative (\( \Delta < 0 \)), there are **no real x-intercepts**. Instead, the roots are complex. **Complex Roots:** \[ x = \frac{-3 \pm \sqrt{-31}}{-4} = \frac{-3 \pm i\sqrt{31}}{-4} = \frac{3}{4} \mp \frac{i\sqrt{31}}{4} \] ### 6. **Plotting the Parabola** Given the above information: - **Vertex:** \( \left( \frac{3}{4}, -\frac{31}{8} \right) \) - **Axis of Symmetry:** \( x = \frac{3}{4} \) - **Y-intercept:** \( (0, -5) \) - **No Real X-intercepts** - **Opens Downward** The parabola will have its highest point at the vertex and will not cross the x-axis. ### 7. **Summary of Key Features** - **Standard Form:** \( y = -2x^{2} + 3x - 5 \) - **Vertex:** \( \left( \frac{3}{4}, -\frac{31}{8} \right) \) - **Axis of Symmetry:** \( x = \frac{3}{4} \) - **Direction:** Opens downward - **Y-intercept:** \( (0, -5) \) - **X-intercepts:** None (Complex roots) If you have a specific question or need further analysis related to this quadratic function, feel free to ask!

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Beyond the Answer

Did you know that the equation \( y = -2x^2 + 3x - 5 \) represents a parabola? Specifically, it's a downward-opening parabola because of the negative coefficient in front of \( x^2 \). The vertex of this parabola is where it reaches its maximum value, and it can be found using the formula \( x = -\frac{b}{2a} \) where \( a \) and \( b \) are the coefficients of \( x^2 \) and \( x \), respectively. For this equation, the vertex will give you important information about the graph! In real-world applications, quadratic equations like this one can model various phenomena, such as projectile motions, profit maximization in businesses, or even designing parabolic reflectors! For instance, if this equation were modeling the profit of a company based on the number of products sold, understanding where the maximum profit occurs (the vertex) can help business owners make informed decisions on pricing and output levels.

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