Answer
$x=\frac{24}{4}=6 $
or
$x=-\frac{5}{2}$
Work Step by Step
$f(x)=0$
$2x^2-7x-30=0$ ($a=2,b=-7,c=-30$):
$x=\frac{-b±\sqrt {b^2-4ac}}{2a}=\frac{-(-7)±\sqrt {(-7)^2-4(2)(-30)}}{2(2)}=\frac{7±\sqrt {289}}{4}=\frac{7±17}{4}$
$x=\frac{24}{4}=6 $
or
$x=\frac{-10}{4}=-\frac{5}{2}$