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What are the solutions to the equation [tex]$x^2 - 1 = 399$[/tex]?

A. [tex]$x = 20$[/tex] and [tex][tex]$x = -20$[/tex][/tex]
B. [tex]$x = 200$[/tex] and [tex]$x = -200$[/tex]
C. [tex][tex]$x = 400$[/tex][/tex] and [tex]$x = -400$[/tex]
D. [tex]$x = \sqrt{398}$[/tex] and [tex][tex]$x = -\sqrt{398}$[/tex][/tex]


Sagot :

To solve the equation [tex]\(x^2 - 1 = 399\)[/tex], follow these steps:

1. Rewrite the Equation: First, we need to isolate the [tex]\(x^2\)[/tex] term. To do this, add 1 to both sides of the equation:
[tex]\[ x^2 - 1 + 1 = 399 + 1 \][/tex]
Simplifying this, we get:
[tex]\[ x^2 = 400 \][/tex]

2. Solve for [tex]\(x\)[/tex]: The next step is to solve for [tex]\(x\)[/tex]. We take the square root of both sides of the equation:
[tex]\[ x = \pm \sqrt{400} \][/tex]

3. Calculate the Square Root: Calculate the square root of 400:
[tex]\[ \sqrt{400} = 20 \][/tex]
Therefore,
[tex]\[ x = \pm 20 \][/tex]
This means [tex]\(x\)[/tex] can either be positive 20 or negative 20.

So, the solutions to the equation [tex]\(x^2 - 1 = 399\)[/tex] are:
[tex]\[ x = 20 \quad \text{and} \quad x = -20 \][/tex]

Hence, the correct answer is:

A. [tex]\(x = 20\)[/tex] and [tex]\(x = -20\)[/tex].