Phân tích đa thức thành nhân tử: x^2 + 5x – 2

x² + 5x – 2

\( = {x^2} + 2.\frac{5}{2}x + \frac{{25}}{4} - \frac{{25}}{4} - 2\)

\( = {\left( {x + \frac{5}{2}} \right)^2} - \frac{{33}}{4}\)

\( = {\left( {x + \frac{5}{2}} \right)^2} - {\left( {\frac{{\sqrt {33} }}{2}} \right)^2}\)

\( = \left( {x + \frac{{5 + \sqrt {33} }}{2}} \right)\left( {x + \frac{{5 - \sqrt {33} }}{2}} \right)\)