Answer:
(x - sqrt(7))(x + sqrt(7))(x - sqrt(3))(x + sqrt(3))
Step-by-step explanation:
x⁴ - 10x² + 21 = 0
Let t = x²
Then the equation becomes,
t² - 10t + 21 = 0
t² - 7t - 3t + 21 = 0
t(t - 7) -3(t - 7l
(t - 7)(t - 3)
Since t = x²,
(x² - 7)(x² - 3)
Using a² - b² = (a - b)(a + b)
(x - sqrt(7))(x + sqrt(7))(x - sqrt(3))(x + sqrt(3))
sqrt : square root
x = +/- sqrt(7) & +/- sqrt(3)
