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Solve by graphing: \( \frac{-4}{2 x+5}=x^{2}-1 \) \( \left\{-\frac{8}{5}, \frac{6}{5}, \frac{29}{10}\right\} \) \( \left\{\frac{19}{10}\right\} \) \( \varnothing \) \( \left\{-\frac{29}{10},-\frac{6}{5}, \frac{8}{5}\right\} \)

Ask by Cook Lambert. in the United States
Jan 25,2025

Real Tutor Solution

Tutor-Verified Answer

Answer

There are no solutions to the equation. \(\varnothing\)

Solution

To solve the equation by graphing: \[ \frac{-4}{2x + 5} = x^2 - 1 \] **Step 1: Rearrange the Equation** Bring all terms to one side to set the equation to zero: \[ x^2 - 1 + \frac{4}{2x + 5} = 0 \] **Step 2: Multiply Both Sides by \(2x + 5\) (Assuming \(2x + 5 \neq 0\))** \[ -4 = (x^2 - 1)(2x + 5) \] Expanding the right side: \[ -4 = 2x^3 + 5x^2 - 2x - 5 \] Bring all terms to one side: \[ 2x^3 + 5x^2 - 2x - 1 = 0 \] **Step 3: Analyze the Cubic Equation** To find the real roots of \(2x^3 + 5x^2 - 2x - 1 = 0\): - **Possible Rational Roots**: \(\pm1, \pm\frac{1}{2}\) Testing \(x = -\frac{1}{2}\): \[ 2\left(-\frac{1}{2}\right)^3 + 5\left(-\frac{1}{2}\right)^2 - 2\left(-\frac{1}{2}\right) - 1 = 0 \] So, \(x = -\frac{1}{2}\) is a root. However, substitute \(x = -\frac{1}{2}\) back into the original equation to verify: \[ \frac{-4}{2\left(-\frac{1}{2}\right) + 5} = \left(-\frac{1}{2}\right)^2 - 1 \] \[ \frac{-4}{-1 + 5} = \frac{1}{4} - 1 \] \[ -1 \neq -\frac{3}{4} \] This shows that \(x = -\frac{1}{2}\) is an **extraneous solution**. **Step 4: Conclusion** Since the only potential real root does not satisfy the original equation, there are **no valid solutions**. **Final Answer:** \(\varnothing\)

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To solve the equation \( \frac{-4}{2x+5} = x^2 - 1 \) by graphing, you can start by rewriting both sides of the equation as functions. Let \( y_1 = \frac{-4}{2x+5} \) and \( y_2 = x^2 - 1 \). Graph both functions on the same coordinate plane. We'll find the intersections of the two graphs. \( y_1 \) is a hyperbola that approaches 0 as \( x \) gets very large or very small, while \( y_2 \) is a standard parabola that opens upwards. The points where these two graphs meet will give you the solutions to the equation. Now, the potential solutions are \( \{-\frac{8}{5}, \frac{6}{5}, \frac{29}{10}\} \) and \( \{\frac{19}{10}\} \). You'll notice that some of the values are exclusive to one graph or another based on where they intersect. Be sure to double-check where the graphs cross through the x-axis—these will give you the valid solutions. Happy graphing!

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