Question

1,Tìm x thuộc Q biết

a,\(\left(3x-1\right)^4=81\)

b,\(\left(x+1\right)^5=32\)

Answer 1

a) (3x - 1)⁴ = 81

=> (3x - 1)⁴ = 3⁴

=> 3x - 1 = 3

=> 3x = 4

=> x = 4/3

b) (x + 1)⁵ = 32

=> (x + 1)⁵ = 2⁵

=> x + 1 = 2

=> x = 1

Answer 2

a) (3x - 1)⁴ = 81

⇔ \(\left[{}\begin{matrix}\left(3x-1\right)^4=3^4\\\left(3x-1\right)^4=\left(-3\right)^4\end{matrix}\right.\)

⇔ \(\left[{}\begin{matrix}3x-1=3\\3x-1=-3\end{matrix}\right.\)

⇔ \(\left[{}\begin{matrix}3x=3+1\\3x=-3+1\end{matrix}\right.\)

⇔ \(\left[{}\begin{matrix}3x=4\\3x=-2\end{matrix}\right.\)

⇔ \(\left[{}\begin{matrix}x=\dfrac{4}{3}\\x=\dfrac{-2}{3}\end{matrix}\right.\)

b) (x + 1)⁵ = 32

⇔ (x + 1)⁵ = 2⁵

⇔ x + 1 = 2

⇔ x = 2 - 1

⇔ x = 1

Answer 3

1,Tìm x thuộc Q biết

a,

(3x−1)⁴ = (-3)⁴

=> 3x - 1 = -3

3x = -3 + 1

3x = -2.

x = -2 : 3

x = \(\dfrac{-2}{3}\)

Vậy x = \(\dfrac{-2}{3}\)

b,

(x+1)⁵= 2⁵

=> x+1= 2

x = 2-1

x = 1.

Vậy x = 1.