Nghiệm kép nên [tex]b^2=4ac\Rightarrow c=\dfrac{b^2}{4a}[/tex]
[tex]f(x)=ax^2+bx+\dfrac{b^2}{4a}=\left ( \sqrt{a}.x+\dfrac{b}{2\sqrt{a}} \right )^2[/tex]
Nghiệm kép nên [tex]b^2=4ac\Rightarrow c=\dfrac{b^2}{4a}[/tex]
[tex]f(x)=ax^2+bx+\dfrac{b^2}{4a}=\left ( \sqrt{a}.x+\dfrac{b}{2\sqrt{a}} \right )^2[/tex]