f(x) = 4x^2+5x-9
Gf∩Ox => y = 0 => f(x) = 0
4x^2+5x-9=0
Δ=5^2-4*4*(-9) = 25 + 144 = 169
[tex]x_{1,2}=\frac{-5+/-\sqrt{169}}{8}\\x_{1} = \frac{-5+\sqrt{169}}{8}=\frac{-5+13}{8}=1=> A(1,0)\\x_{2} = \frac{-5-\sqrt{169}}{8}=\frac{-5-13}{8}=\frac{-18}{8}=\frac{-9}{4}=>B(\frac{-9}{4},0)[/tex]
