One of the solutions to the equation x3+5x2+10x+50=0

𝑥
3
+
5
𝑥
2
+
10
𝑥
+
50
=
0
is −5

5
. Find the full solution set. Which of the following options correctly describes the solution set?

Option #1: It has one real solution and two non-real solutions.

Option #2: It has one non-real solution and two real solutions.

Option #3: It has three real solutions.

1 answer

To find the full solution set for the polynomial equation \( x^3 + 5x^2 + 10x + 50 = 0 \) given that one solution is \( x = -5 \), we can first use polynomial long division or synthetic division to factor the polynomial by \( x + 5 \).

Step 1: Synthetic division

Perform synthetic division with \( x = -5 \):

-5 |  1   5   10   50
   |      -5   0  -50
----------------------
     1   0   10    0

This gives us the quotient \( x^2 + 10 \) (the remainder is \( 0 \)), meaning we can factor the original cubic equation as:

\[ x^3 + 5x^2 + 10x + 50 = (x + 5)(x^2 + 10) \]

Step 2: Solve the quadratic factor

Now, we solve the quadratic equation \( x^2 + 10 = 0 \):

\[ x^2 = -10 \]

Taking the square root of both sides, we get:

\[ x = \pm i\sqrt{10} \]

Step 3: Summary of solutions

Thus, the full solution set for the equation \( x^3 + 5x^2 + 10x + 50 = 0 \) is:

\[ x = -5, \quad x = i\sqrt{10}, \quad x = -i\sqrt{10} \]

Step 4: Identify the nature of the solutions

  • One real solution: \( -5 \)
  • Two non-real solutions: \( i\sqrt{10} \) and \( -i\sqrt{10} \)

Conclusion:

The correct option that describes the solution set is:

Option #1: It has one real solution and two non-real solutions.