Which shows the correct substitution of the values [tex]\( a, b \)[/tex], and [tex]\( c \)[/tex] from the equation [tex]\( -2 = -x + x^2 - 4 \)[/tex] into the quadratic formula?

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

A. [tex]\[ x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(1)(-4)}}{2(1)} \][/tex]

B. [tex]\[ x = \frac{-1 \pm \sqrt{1^2 - 4(-1)(-4)}}{2(-1)} \][/tex]

C. [tex]\[ x = \frac{-1 \pm \sqrt{(1)^2 - 4(-1)(-2)}}{2(-1)} \][/tex]

D. [tex]\[ x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(1)(-2)}}{2(1)} \][/tex]



Answer :

To find the correct substitution of the values [tex]\(a\)[/tex], [tex]\(b\)[/tex], and [tex]\(c\)[/tex] into the quadratic formula, let's start by rewriting the given equation [tex]\(-2 = -x + x^2 - 4\)[/tex] in the standard quadratic form [tex]\(ax^2 + bx + c = 0\)[/tex].

First, rewrite the equation:
[tex]\[ -2 = -x + x^2 - 4 \][/tex]

Move all terms to the left side of the equation to set it to [tex]\(0\)[/tex]:
[tex]\[ x^2 - x - 4 + 2 = 0 \][/tex]

Simplify it:
[tex]\[ x^2 - x - 2 = 0 \][/tex]

Here, [tex]\(a = 1\)[/tex], [tex]\(b = -1\)[/tex], and [tex]\(c = -2\)[/tex].

Now, substitute these values into the quadratic formula:
[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

Substitute [tex]\(a = 1\)[/tex], [tex]\(b = -1\)[/tex], and [tex]\(c = -2\)[/tex]:
[tex]\[ x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(1)(-2)}}{2(1)} \][/tex]

Simplify it step-by-step:

1. Calculate [tex]\(-b\)[/tex]:
[tex]\[ -(-1) = 1 \][/tex]

2. Calculate the discriminant:
[tex]\[ (-1)^2 - 4(1)(-2) = 1 + 8 = 9 \][/tex]

3. Calculate the square root of the discriminant:
[tex]\[ \sqrt{9} = 3 \][/tex]

4. Substitute these values back into the formula:
[tex]\[ x = \frac{1 \pm 3}{2 \cdot 1} = \frac{1 \pm 3}{2} \][/tex]

So, our solutions are:
[tex]\[ x_1 = \frac{1 + 3}{2} = \frac{4}{2} = 2 \][/tex]
[tex]\[ x_2 = \frac{1 - 3}{2} = \frac{-2}{2} = -1 \][/tex]

Thus, the correct substitution and steps are shown in:
[tex]\[ x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(1)(-2)}}{2(1)} \][/tex]

The correct option is:
\[
x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(1)(-4)}}{2(1)}