[tex]f(x)=ax^2+bx+c=a\left(x+\dfrac{b}{2a}\right)^2-\dfrac{\Delta}{4a}=\\\\=a\left(x+\dfrac{b}{2a}\right)^2-\dfrac{b^2-4ac}{4a}=a\left(x+\dfrac{b}{2a}\right)^2-\dfrac{b^2}{4a}+c;\\\\a=-\dfrac{1}{3},\;b=-\dfrac{2}5,\;c=1\Rightarrow \dfrac{b}{2a}=\left(-\dfrac{2}5\right)\cdot\dfrac{1}2\cdot(-3)=\dfrac{3}5;\\\\-\dfrac{b^2}{4a}=\left(-\dfrac{4}{25}\right)\cdot\dfrac{1}{4}\cdot(-3)=\dfrac3{25}.\text{ Deci forma canonic}\breve{a}\;este:\\\\f(x)=\left(-\dfrac{1}3\right)\cdot\left(x+\dfrac{3}5\right)^2+\dfrac{28}{25}.[/tex]
Green eyes.
