2x^2 + 5x - 4

Phân tích đa thức thành nhân tử.

$\text{→ Ta có :}$

$\text{2x² + 5x - 4}$

$\text{= 2( x² + $\dfrac{5}{2}$x - 2 )}$

$\text{= 2( x² + $\dfrac{5}{2}$x + $\dfrac{25}{16}$ - $\dfrac{57}{16}$ )}$

$\text{= 2[ ( x + $\dfrac{5}{4}$ )² - ( $\dfrac{\sqrt{57}}{4}$ )² ]}$

$\text{= 2( x + $\dfrac{5 + \sqrt{57}}{4}$ )( x + $\dfrac{5 - \sqrt{57}}{4}$ )}$

5 sao nha