Answer:
x = 3.24, x = -1.24
Step-by-step explanation:
The standard form for a quadratic equation is [tex]ax^2+bx+c=0[/tex]. For your equation a = 1, b = -2, c = -4. The quadratic formula you will be using is [tex]x=\frac{-b\pm \sqrt{b^{2} -4ac} }{2a}[/tex].
Plug in a = 1, b = -2, and c = -4 into the formula.
[tex]=\frac{-\left(-2\right)\pm \sqrt{\left(-2\right)^2-4\cdot \:1\cdot \left(-4\right)}}{2\cdot \:1}[/tex]
We'll do the top part first:
[tex]\sqrt{\left(-2\right)^2-4\cdot \:1\cdot \left(-4\right)}[/tex]
Apply rule [tex]- (-a) = a[/tex]
[tex]=\sqrt{\left(-2\right)^2+4\cdot \:1\cdot \:4}[/tex]
Apply exponent rule [tex](-a)^{n} =a^n[/tex] if [tex]n[/tex] is even
[tex](-2)^2=2^2[/tex]
[tex]=\sqrt{2^2+4\cdot \:1\cdot \:4}[/tex]
Multiply the numbers
[tex]=\sqrt{2^2+16}[/tex]
[tex]2^2=4[/tex]
[tex]=\sqrt{4+16}[/tex]
Add
[tex]=\sqrt{20}[/tex]
The prime factorization of 20 is [tex]2^2*5[/tex]
20 divides by 2. 20 = 10 * 2
[tex]=2*10[/tex]
10 divides by 2. 10 = 5 * 2
[tex]=2* \:2*5[/tex]
2 & 5 are prime numbers so you don't need to factor them anymore
[tex]=2*2*5[/tex]
[tex]=2^2*5[/tex]
[tex]=\sqrt{2^2\cdot \:5}[/tex]
Apply radical rule [tex]\sqrt[n]{ab} =\sqrt[n]{a} \sqrt[n]{b}[/tex]
[tex]=\sqrt{5}\sqrt{2^2}[/tex]
Apply radical rule [tex]\sqrt[n]{a^{n} } =a[/tex]; [tex]\sqrt{2^2} =2[/tex]
[tex]=2\sqrt{5}[/tex]
[tex]=\frac{-\left(-2\right)\pm \:2\sqrt{5}}{2\cdot \:1}[/tex]
Because of the [tex]\pm[/tex] you have to separate the solutions so that one is positive and the other is negative.
[tex]x=\frac{-\left(-2\right)+2\sqrt{5}}{2\cdot \:1},\:x=\frac{-\left(-2\right)-2\sqrt{5}}{2\cdot \:1}[/tex]
Positive x:
[tex]\frac{-\left(-2\right)+2\sqrt{5}}{2\cdot \:1}[/tex]
Apply rule [tex]-(-a)=a[/tex]
[tex]=\frac{2+2\sqrt{5}}{2\cdot \:1}[/tex]
Multiply
[tex]=\frac{2+2\sqrt{5}}{2}[/tex]
Factor [tex]2+2\sqrt{5}[/tex] and rewrite it as [tex]=2\cdot \:1+2\sqrt{5}[/tex]. Factor out 2 because it is the common term. [tex]=2\left(1+\sqrt{5}\right)[/tex].
[tex]=\frac{2\left(1+\sqrt{5}\right)}{2}[/tex]
Divide 2 by 2
[tex]x=1+\sqrt{5}[/tex] or [tex]x=3.24[/tex] (You'll probably have to use a calculator for the square root of 5)
^Repeating the process of positive x for negative x in order to get [tex]x=1-\sqrt{5}[/tex] or [tex]x=-1.24[/tex]
