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Use the work shown to find the solutions of the quadratic equation.

[tex]\[
\begin{array}{l}
x^2 - x - \frac{3}{4} = 0 \\
x^2 - x = \frac{3}{4}
\end{array}
\][/tex]

[tex]\[
\begin{array}{l}
x^2 - x + \left(\frac{1}{2}\right)^2 = \frac{3}{4} + \left(\frac{1}{2}\right)^2 \\
x^2 - x + \frac{1}{4} = \frac{3}{4} + \frac{1}{4}
\end{array}
\][/tex]

Which is a solution of \( x^2 - x - \frac{3}{4} = 0 \)?

A. \(-\frac{1}{4}\)

B. \(\frac{1}{2}\)

C. \(\frac{3}{2}\)

D. [tex]\(\frac{3}{4}\)[/tex]


Sagot :

Let's solve the quadratic equation step-by-step, using the quadratic equation provided:

[tex]\[ x^2 - x - \frac{3}{4} = 0 \][/tex]

First, we'll rewrite the equation by moving \(-\frac{3}{4}\) to the other side:

[tex]\[ x^2 - x = \frac{3}{4} \][/tex]

Next, to make this suitable for completing the square, we add \(\left(\frac{1}{2}\right)^2\) to both sides. This is because the coefficient of \(x\) is \(-1\), and half of \(-1\) is \(-\frac{1}{2}\), so when squared, it is \(\left(\frac{1}{2}\right)^2\):

[tex]\[ x^2 - x + \left(\frac{1}{2}\right)^2 = \frac{3}{4} + \left(\frac{1}{2}\right)^2 \][/tex]

Calculating the right-hand side:

[tex]\[ x^2 - x + \frac{1}{4} = \frac{3}{4} + \frac{1}{4} \][/tex]
[tex]\[ x^2 - x + \frac{1}{4} = 1 \][/tex]

The left-hand side is now a perfect square trinomial:

[tex]\[ (x - \frac{1}{2})^2 = 1 \][/tex]

To find \(x\), we take the square root of both sides:

[tex]\[ x - \frac{1}{2} = \pm 1 \][/tex]

This gives us two equations to solve:

[tex]\[ x - \frac{1}{2} = 1 \quad \text{or} \quad x - \frac{1}{2} = -1 \][/tex]

Solving these:

[tex]\[ x = 1 + \frac{1}{2} = \frac{3}{2} \][/tex]
[tex]\[ x = -1 + \frac{1}{2} = -\frac{1}{2} \][/tex]

Therefore, the solutions to the quadratic equation \(x^2 - x - \frac{3}{4} = 0\) are:

[tex]\[ x = \frac{3}{2} \quad \text{and} \quad x = -\frac{1}{2} \][/tex]

From the given possible solutions:

- \(-\frac{1}{4}\)
- \(\frac{1}{2}\)
- \(\frac{3}{2}\)
- \(\frac{3}{4}\)

The correct solution provided by the options is \(\frac{3}{2}\).

Thus, the solution of \(x^2 - x - \frac{3}{4} = 0\) from the options given is:

[tex]\[ \boxed{\frac{3}{2}} \][/tex]