Question

4x2 – 15 = 85
I don’t understand this

Answer 1

1.) x = 5

2.) x = -5

Explanation:

(22x2 - 15) - 85 = 0

4x2 - 100 = 4 • (x2 - 25)

(x + 5) • (x - 5)

4 • (x + 5) • (x - 5) = 0

x+5 = 0

x = -5

x-5 = 0