2 x^2 – 72 = 0 giúp mik vs hứa vote 5 sao ạ

2 x^2 – 72 = 0

2 ( x^2 – 36 ) = 0

x^2 – 36 = 0

x^2 – 6^2 = 0

( x – 6 ) . ( x + 6 ) = 0

suy ra:

1) x – 6 = 0

         x = 6

2) x + 6 = 0

          x = -6

                        Vậy x = 6 hoặc x = -6