Question

3) If 4x2 - 100 = 0, what are the roots of the

equation?
1) -5 and 5
2)-25, only
3)-5, only
4) -25 and 25

Answer 1

Hello !

4x² - 100 = 0

We have a² - b² = (a + b)(a - b)

so 4x² - 100 = 0

⇔ (2x)² - 10² = 0

⇔ (2x + 10)(2x - 10) = 0

2x + 10 = 0 or 2x - 10 = 0

2x = - 10 or 2x = 10

x = -10/2 or x = 10/2

x = -5 or x = 5