Question

X^4-13x^2+36=0 x=???

Answer 1

x⁴ - 13x² + 36 = 0

t² - 13t + 36 = 0

t = 4, t = 9

x² = 4, x² = 9

x = ±2, x = ±3

Answer 2

-3,-2,3,2

Explanation:

Let a = x^2

Then the equation turns into

a^2 - 13 a + 36 =0

a^2 - 4a - 9a + 36 = 0

a(a - 4) -9 (a -4) =0

(a-9)(a-4) = 0

a = 9 or a = 4

So

x^2 = 9 or x^2 = 4

Therefore x = -3,3 or x= -2,2.