Question

(x + 2)(x² - x + 2)=0

Answer 1

Ta có :

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

\(\left(x+2\right).\left[\left(x^2-2.\frac{1}{2}x+\frac{1}{4}\right)+\frac{7}{4}\right]=0\)

\(\left(x+2\right)\left[\left(x-\frac{1}{2}\right)^2+\frac{7}{4}\right]=0\)

Mà \(\left(x-\frac{1}{2}\right)^2\ge0\)

\(\Rightarrow\left(x-\frac{1}{2}\right)^2+\frac{7}{4}\ge\frac{7}{4}\)

\(\Rightarrow\left(x-\frac{1}{2}\right)^2+\frac{7}{4}>0\)

\(\Rightarrow x+2=0\)

\(\Rightarrow x=-2\)