What are the solutions of [tex]$x^2 + 121 = 0$[/tex]?

A. [tex]-11, 11[/tex]
B. [tex]11, 11i[/tex]
C. [tex]11, -11i[/tex]
D. [tex]-11i, 11i[/tex]



Answer :

To solve the quadratic equation [tex]\( x^2 + 121 = 0 \)[/tex], let's follow a step-by-step approach:

1. Rewrite the equation:
[tex]\[ x^2 + 121 = 0 \][/tex]

2. Isolate [tex]\( x^2 \)[/tex] by subtracting [tex]\( 121 \)[/tex] from both sides:
[tex]\[ x^2 = -121 \][/tex]

3. Take the square root of both sides:
[tex]\[ x = \pm\sqrt{-121} \][/tex]

4. Simplify the expression under the square root:
Notice that [tex]\( -121 \)[/tex] can be written as [tex]\( -1 \times 121 \)[/tex]. Therefore,
[tex]\[ \sqrt{-121} = \sqrt{-1 \times 121} = \sqrt{-1} \times \sqrt{121} \][/tex]

5. Use the fact that [tex]\( \sqrt{-1} \)[/tex] is defined as [tex]\( i \)[/tex] (the imaginary unit):
[tex]\[ \sqrt{-121} = i \times 11 = 11i \][/tex]

6. So, the solutions will be:
[tex]\[ x = \pm 11i \][/tex]

Thus, the solutions to the equation [tex]\( x^2 + 121 = 0 \)[/tex] are [tex]\( 11i \)[/tex] and [tex]\( -11i \)[/tex], which corresponds to option:

D. [tex]\( -11i, 11i \)[/tex]