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7. \( 3 x^{2}-21=4-x^{2} \)

Ask by Reed Mckenzie. in the United States
Mar 20,2025

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Tutor-Verified Answer

Answer

The solutions are \( x = -2.5 \) and \( x = 2.5 \).

Solution

Solve the equation \( 3x^{2}-21=4-x^{2} \). Solve the quadratic equation by following steps: - step0: Solve using square roots: \(3x^{2}-21=4-x^{2}\) - step1: Add or subtract both sides: \(4x^{2}=25\) - step2: Divide both sides: \(\frac{4x^{2}}{4}=\frac{25}{4}\) - step3: Divide the numbers: \(x^{2}=\frac{25}{4}\) - step4: Simplify the expression: \(x=\pm \sqrt{\frac{25}{4}}\) - step5: Simplify the expression: \(x=\pm \frac{5}{2}\) - step6: Separate into possible cases: \(\begin{align}&x=\frac{5}{2}\\&x=-\frac{5}{2}\end{align}\) - step7: Rewrite: \(x_{1}=-\frac{5}{2},x_{2}=\frac{5}{2}\) The solutions to the equation \(3x^{2}-21=4-x^{2}\) are \(x=-\frac{5}{2}\) and \(x=\frac{5}{2}\), which can also be written as \(x=-2.5\) and \(x=2.5\).

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Bonus Knowledge

To solve the equation \( 3 x^{2}-21=4-x^{2} \), we start by moving all terms to one side to set the equation to zero: \[ 3x^2 + x^2 - 21 - 4 = 0 \] This simplifies to: \[ 4x^2 - 25 = 0 \] Now, we can add 25 to both sides: \[ 4x^2 = 25 \] Next, divide both sides by 4: \[ x^2 = \frac{25}{4} \] Taking the square root of both sides gives us: \[ x = \pm \frac{5}{2} \] Thus, the solutions are: \[ x = \frac{5}{2} \quad \text{and} \quad x = -\frac{5}{2} \] The solutions can also be expressed as decimal values: \( 2.5 \) and \( -2.5 \). Happy solving!

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