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What are the exact solutions of [tex]$x^2 - 5x - 1 = 0[tex]$[/tex] using [tex]$[/tex]x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$[/tex]?

A. [tex]$x = \frac{5 \pm \sqrt{29}}{2}$[/tex]
B. [tex]$x = \frac{-5 \pm \sqrt{29}}{2}$[/tex]
C. [tex]$x = \frac{5 \pm \sqrt{21}}{2}$[/tex]
D. [tex]$x = \frac{-5 \pm \sqrt{21}}{2}$[/tex]

Sagot :

To find the exact solutions of the quadratic equation \(x^2 - 5x - 1 = 0\), we use the quadratic formula:

[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

In this equation, \(a = 1\), \(b = -5\), and \(c = -1\).

Using these values, we can follow these steps:

1. Identify the coefficients:
[tex]\[ a = 1, \quad b = -5, \quad c = -1 \][/tex]

2. Calculate the discriminant:
[tex]\[ \Delta = b^2 - 4ac = (-5)^2 - 4 \cdot 1 \cdot (-1) = 25 + 4 = 29 \][/tex]

3. Substitute the coefficients and the discriminant into the quadratic formula:
[tex]\[ x = \frac{-b \pm \sqrt{\Delta}}{2a} = \frac{-(-5) \pm \sqrt{29}}{2 \cdot 1} = \frac{5 \pm \sqrt{29}}{2} \][/tex]

Therefore, the exact solutions of the equation \(x^2 - 5x - 1 = 0\) are:
[tex]\[ x = \frac{5 \pm \sqrt{29}}{2} \][/tex]

This corresponds to the solution:
[tex]\[ x = \frac{5 \pm \sqrt{29}}{2} \][/tex]