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Which of the following are solutions to the quadratic equation below? Check all that apply.

[tex] x^2 + 2x - 8 = 0 [/tex]

A. -1
B. 6
C. -4
D. 2
E. 8


Sagot :

To determine which of the given options are solutions to the quadratic equation [tex]\( x^2 + 2x - 8 = 0 \)[/tex], we'll need to solve the equation and then check each option against the solutions.

### Step-by-Step Solution:

1. Write down the quadratic equation:
[tex]\[ x^2 + 2x - 8 = 0 \][/tex]

2. Solve the quadratic equation:
The solutions to a quadratic equation [tex]\( ax^2 + bx + c = 0 \)[/tex] are found using the quadratic formula:
[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]
In this equation, [tex]\( a = 1 \)[/tex], [tex]\( b = 2 \)[/tex], and [tex]\( c = -8 \)[/tex].

3. Calculate the discriminant:
[tex]\[ \Delta = b^2 - 4ac = 2^2 - 4(1)(-8) = 4 + 32 = 36 \][/tex]

4. Plug the discriminant back into the quadratic formula:
[tex]\[ x = \frac{-2 \pm \sqrt{36}}{2 \cdot 1} = \frac{-2 \pm 6}{2} \][/tex]

5. Find the two solutions:
[tex]\[ x = \frac{-2 + 6}{2} = \frac{4}{2} = 2 \][/tex]
[tex]\[ x = \frac{-2 - 6}{2} = \frac{-8}{2} = -4 \][/tex]

Thus, the solutions to the quadratic equation [tex]\( x^2 + 2x - 8 = 0 \)[/tex] are [tex]\( x = 2 \)[/tex] and [tex]\( x = -4 \)[/tex].

### Check the Given Options:

Let's check each of the given options to see if they match the solutions [tex]\( x = 2 \)[/tex] and [tex]\( x = -4 \)[/tex]:

- A. [tex]\(-1\)[/tex]: [tex]\(-1\)[/tex] is not in the list of solutions.
- B. [tex]\(6\)[/tex]: [tex]\(6\)[/tex] is not in the list of solutions.
- C. [tex]\(-4\)[/tex]: [tex]\(-4\)[/tex] is a solution.
- D. [tex]\(2\)[/tex]: [tex]\(2\)[/tex] is a solution.
- E. [tex]\(8\)[/tex]: [tex]\(8\)[/tex] is not in the list of solutions.

### Summary:

The options that are solutions to the quadratic equation [tex]\( x^2 + 2x - 8 = 0 \)[/tex] are:

- [tex]\( C. -4 \)[/tex]
- [tex]\( D. 2 \)[/tex]

So, the correct options are [tex]\( \boxed{C} \)[/tex] and [tex]\( \boxed{D} \)[/tex].