Question

What are the solutions to the equation x2 − 1 = 399?

Answer 1

x = ±20

Explanation:

x² - 1 = 399

x² = 400

x = ±√(400)

x = ±20

Answer 2

Hello !

Answer:

`\boxed{\sf x=\pm 20}`

Explanation:

We want to solve the following equation :

`x^2-1=399`

Let's add 1 to both sides :

`x^2-1+1=399+1\\x^2=400`

We know that if
`x^2=a` (assuming
`a\geq 0`), then
`x=\pm\sqrt a`.

Let's apply this to our equation :

`\sf x=\pm \sqrt {400}\\x=20\ \sf{or}\ x=-20`

This equation has two solutions: x = 20 and x = -20

Have a nice day !