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

a. x=20 and x=-20

b. x=200 and x=-200

c. x=400 and x=-400

d. x=398 squared and x=-398 squared

Good evening ,

Answer :

A.

x = ±20

Step-by-step explanation:

x² − 1 = 399 ⇔ x²= 400 ⇌ x² = 20² ⇌ x² − 20² = 0 ⇌ (x-20)(x+20) = 0

⇌ x = 20 or x = -20.

:)

answer: what are the following choices