[tex]\displaystyle 4x^2+9x-9=0 \\ a=4,b=9,c=-9 \\ \Delta=b^2-4ac=9^2-4 \cdot 4 \cdot (-9)=81+144=225 \\ x_1= \frac{-9+ \sqrt{225} }{2 \cdot 4} = \frac{-9+15}{8} = \frac{6}{8} = \frac{3}{4} \\ \\ x_2= \frac{-9- \sqrt{225} }{2 \cdot 4} = \frac{-9-15}{8} = \frac{-24}{8} =-3[/tex]
