Question

cho hàm số y = f ( x ) = | 3 x - 1 | - 2 tìm x sao cho f ( x ) = 3

 

Answer 1

Ta có: f(x) = 3 => y = 3

Thay vào ta có:

\(\left|3x-1\right|-2\) = 3

=> \(\Rightarrow\left|3x-1\right|=3+2=5\)

+) 3x - 1 = 5

=> 3x = 5 + 1 = 6

=> x = \(\frac{6}{3}=2\)

+) 3x - 1 = -5

=> 3x = -5 + 1 = -4

=> x = \(\frac{-4}{3}\)

Vậy x = 2 hoặc x = \(\frac{-4}{3}\)

 

Answer 2

Ta có: \(y=f\left(x\right)=\left|3x-1\right|-2\)

Khi \(f\left(x\right)=3\) thì \(3=\left|3x-1\right|-2\)

\(\Rightarrow\left|3x-1\right|=5\)

\(\Rightarrow3x-1=\pm5\)

+) \(3x-1=5\Rightarrow x=2\)

+) \(3x-1=-5\Rightarrow x=\frac{-4}{3}\)

Vậy \(x\in\left\{2;\frac{-4}{3}\right\}\)