Question

1 . ( 2x² - 1) ²  - ( x+1 ) ² = 0

2 . 27x³ -54x² + 36x =9

3 . x² + 8x + 7 = 0

 

Answer 1

1: \(\Leftrightarrow\left(2x^2-1-x-1\right)\left(2x^2-1+x+1\right)=0\)

\(\Leftrightarrow\left(2x^2-x-2\right)\left(2x^2+x\right)=0\)

hay \(x\in\left\{0;-\dfrac{1}{2};\dfrac{1+\sqrt{17}}{4};\dfrac{1-\sqrt{17}}{4}\right\}\)

3: =>(x+7)(x+1)=0

=>x=-7 hoặc x=-1