To find the points that fullfil the equation:
[tex]f(x)=-4[/tex]we plug the expression for the function and solve for x, then:
[tex]\begin{gathered} 8x^2-18x+5=-4 \\ 8x^2-18x+9=0 \\ x=\frac{-(-18)\pm\sqrt[]{(-18)^2-4(8)(9)}}{2(8)} \\ x=\frac{18\pm\sqrt[]{324-288}}{16} \\ x=\frac{18\pm\sqrt[]{36}}{16} \\ x=\frac{18\pm6}{16} \\ x_1=\frac{18+6}{16}=\frac{24}{16}=\frac{3}{2} \\ x_2=\frac{18-6}{16}=\frac{12}{16}=\frac{3}{4} \end{gathered}[/tex]Therefore the points are (3/2,-4) and (3/4,-4).
