Answer:
The correct answer is "B", we first need to add 40 to both sides of the equation.
Step-by-step explanation:
Since we have the following quadratic equation:
[tex]x^2 - 40 = 0[/tex]
The first step to solve it is to isolate the independent variable, "x". To do that we must add +40 on both sides of the equation, since that way the "-40" on the left will be gone in a way that maintains the validity of the equation as shown below:
[tex]x^2 - 40 = 0\\x^2 - 40 + 40 = 40\\x^2 = 40[/tex]
After this step we take the square root of both sides:
[tex]\sqrt{x^2} = \sqrt{40}\\x = \pm \sqrt{40}\\x = \pm \sqrt{4*10}\\x = \pm 2*\sqrt{10}[/tex]
Therefore the correct answer is "B".
