Find the real zeros, if any, of each quadratic function using the quadratic formula. List the x-intercepts, if any, of the
graph of the function.
-$$f ( x ) = 5 x ^ { 2 } - 18 x - 8$$
A) $x = - \frac { 2 } { 5 } , x = 4$
B) $x = \frac { 2 } { 5 } , x = - 4$
C) $x = - \frac { 4 } { 5 } , x = 8$
D) $x = - 2 , x = 4$

Question

Quizplus · Accepted Answer

The quadratic formula is $x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$, where $a = 5$, $b = -18$, and $c = -8$. Plugging these values in gives $x = \frac{18 \pm \sqrt{(-18)^2 - 4(5)(-8)}}{2(5)}$, which simplifies to $x = \frac{18 \pm \sqrt{324 + 160}}{10}$ or $x = \frac{18 \pm \sqrt{484}}{10}$. This further simplifies to $x = \frac{18 \pm 22}{10}$, giving $x = -\frac{2}{5}$ and $x = 4$.

Find the Real Zeros, If Any, of Each Quadratic Function f(x)=5x2−18x−8f ( x ) = 5 x ^ { 2 } - 18 x - 8f(x)=5x2−18x−8

Find the Real Zeros, If Any, of Each Quadratic Function $f ( x ) = 5 x ^ { 2 } - 18 x - 8$