Setting the given equation equals -4 we get:
[tex]\begin{gathered} 8x^2-18x+5=-4 \\ 8x^2-18x+5+4=0 \\ 8x^2-18x+9=0 \end{gathered}[/tex]Notice that:
[tex]8x^2-18x+9=8(x^2-\frac{9}{4}x+\frac{9}{8})=8(x-\frac{3}{2})(x-\frac{3}{4})[/tex]Therefore, f(x)=-4 when x=3/2 or x=3/4.
