f(x) = 8x² - 18x + 5
f(x) = -4
replacing f(x) with -4 in the given function:
-4 = 8x² - 18x + 5
8x² - 18x + 5 + 4 = 0
8x² - 18x + 9 = 0
Using the almighty formula:
For ax² +bx + c = 0:
8x² - 18x + 9 = 0
a = 8, b= -18, c = 9
[tex]x\text{ = }\frac{-b\pm\sqrt[]{b^2-4ac}}{2a}[/tex][tex]\begin{gathered} x\text{ = }\frac{-(-18)\pm\sqrt[]{(-18)^2-4(8)(9)}}{2(8)} \\ x\text{ = }\frac{18\pm\sqrt[]{324-288}}{16}=\frac{18\pm\sqrt[]{36}}{16} \end{gathered}[/tex][tex]\begin{gathered} x=\frac{18\pm\sqrt[]{36}}{16}=\frac{18\pm6}{16} \\ x\text{ = }\frac{18+6}{16}or\text{ }\frac{18-6}{16} \\ x\text{ = 24/16 or 12/16} \\ x\text{ = 3/2 or x = 3/4} \end{gathered}[/tex]
