Answer
The expression \( 4x^{2} - 20x - 9 \) can be factored as \( 4\left(x - \frac{5 - \sqrt{34}}{2}\right)\left(x - \frac{5 + \sqrt{34}}{2}\right) \).
Solution
Solve the quadratic equation by following steps:
- step0: Solve using the quadratic formula:
\(4x^{2}-20x-9=0\)
- step1: Solve using the quadratic formula:
\(x=\frac{20\pm \sqrt{\left(-20\right)^{2}-4\times 4\left(-9\right)}}{2\times 4}\)
- step2: Simplify the expression:
\(x=\frac{20\pm \sqrt{\left(-20\right)^{2}-4\times 4\left(-9\right)}}{8}\)
- step3: Simplify the expression:
\(x=\frac{20\pm \sqrt{544}}{8}\)
- step4: Simplify the expression:
\(x=\frac{20\pm 4\sqrt{34}}{8}\)
- step5: Separate into possible cases:
\(\begin{align}&x=\frac{20+4\sqrt{34}}{8}\\&x=\frac{20-4\sqrt{34}}{8}\end{align}\)
- step6: Simplify the expression:
\(\begin{align}&x=\frac{5+\sqrt{34}}{2}\\&x=\frac{20-4\sqrt{34}}{8}\end{align}\)
- step7: Simplify the expression:
\(\begin{align}&x=\frac{5+\sqrt{34}}{2}\\&x=\frac{5-\sqrt{34}}{2}\end{align}\)
- step8: Rewrite:
\(x_{1}=\frac{5-\sqrt{34}}{2},x_{2}=\frac{5+\sqrt{34}}{2}\)
To factor the expression \( 4x^{2} - 20x - 9 \), we first need to find its roots by solving the equation \( 4x^{2} - 20x - 9 = 0 \).
### Step 1: Solve the Quadratic Equation
Using the quadratic formula, we find the roots:
\[
x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
\]
Here, \( a = 4 \), \( b = -20 \), and \( c = -9 \).
Calculating the discriminant:
\[
b^2 - 4ac = (-20)^2 - 4 \cdot 4 \cdot (-9) = 400 + 144 = 544
\]
Now, substituting into the quadratic formula:
\[
x = \frac{20 \pm \sqrt{544}}{8}
\]
### Step 2: Simplify the Roots
The square root of 544 can be simplified:
\[
\sqrt{544} = \sqrt{16 \cdot 34} = 4\sqrt{34}
\]
Thus, the roots are:
\[
x_{1} = \frac{20 - 4\sqrt{34}}{8} = \frac{5 - \sqrt{34}}{2}
\]
\[
x_{2} = \frac{20 + 4\sqrt{34}}{8} = \frac{5 + \sqrt{34}}{2}
\]
### Step 3: Write the Factored Form
Using the roots, we can express the quadratic in its factored form:
\[
4x^{2} - 20x - 9 = 4\left(x - \frac{5 - \sqrt{34}}{2}\right)\left(x - \frac{5 + \sqrt{34}}{2}\right)
\]
### Final Factored Form
Thus, the factored form of \( 4x^{2} - 20x - 9 \) is:
\[
4\left(x - \frac{5 - \sqrt{34}}{2}\right)\left(x - \frac{5 + \sqrt{34}}{2}\right)
\]
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