Question

Tìm số nguyên x , biết:

5) ( 1 + 3x)\(^3\) = 64

6) ( 11 - 4x) \(^3\) = 343

Answer 1

a, \(\left(1+3x\right)^3=64\Leftrightarrow\left(1+3x\right)^3=4^3\)

\(\Leftrightarrow1+3x=4\Leftrightarrow3x=3\Rightarrow x=1\in Z\)

Vậy x = 1

b, \(\left(11-4x\right)^3=343\Leftrightarrow\left(11-4x\right)^3=7^3\)

\(\Leftrightarrow11-4x=7\Rightarrow4x=11-7\Rightarrow4x=4\Rightarrow x=1\in Z\)

Vậy x = 1

Answer 2

1.

( 1 + 3x ) = 64

( 1 + 3x ) = 4³

( 1 + 3x ) = 4

3x = 4 - 1

3x = 3

x = 3 : 3

x = 1

2.

( 11 - 4x )³ = 343

( 11 - 4x )³ = 7³

( 11 - 4x ) = 7

4x = 11 - 7

4x = 4

x = 4 : 4

x = 1