Question

VALOR DE X ///   9x²-81=0

Answer 1

a = 9         b = 0        c = 81

Δ = b² - 4ac
Δ = 0² - 4 * 9 * (-81)
Δ = 0 + 2916
Δ = 2916

x = (-b +/- √Δ) / 2 *a
x = (-0 +/- √2916) / 2 * 9
x = (0 +/- 54) / 18

x' = (0 + 54) / 18 
x' = 54 / 18
x' = 3

x" = (0 - 54) / 18
x" = -54 / 18
x" = -3

Answer 2

9x² - 81 = 0

9x²= 0 + 81

9x²= 81

x²= 81/9

x²= 9

x= ± √9

x= ± 3

S= ( 3 , - 3)