Tìm x, biết: c) (5x – 6)3 = 64; d) (3x)3 = (2x + 1)3.

c) (5x – 6)³ = 64

Vì 64 = 4³. Khi đó ta có

(5x – 6)³ = 4³

Suy ra 5x – 6 = 4

           5x = 10

           x = 2

Vậy x = 2.

d) (3x)³ = (2x + 1)³

Suy ra 3x = 2x + 1

          3x – 2x = 1

          x = 1

Vậy x = 1.