Solve x^4 – 10x^2 + 9 = 0 (MULTIPLE CHOICE)

Question

Solve x⁴ – 10x² + 9 = 0

 

a. x = ±1 or x = ±i√3
b. x = ±3 or x = ±i
c. x = ±3 or x = ±i√10
d. x = ±1 or x = ±3

Answer 1

x⁴ -10x² + 9 = 0

 

(x² - 1)(x² - 9)  = 0

 

(x + 1)(x - 1)(x - 3)(x + 3) = 0

 

x = -1, 1, 3, -3