What are the zeros of the quadratic function [tex]f(x)=2x^2 + 16x - 9[/tex]?

A. [tex]x = -4 - \sqrt{\frac{7}{2}}[/tex] and [tex]x = -4 + \sqrt{\frac{7}{2}}[/tex]

B. [tex]x = -4 - \sqrt{\frac{25}{2}}[/tex] and [tex]x = -4 + \sqrt{\frac{25}{2}}[/tex]

C. [tex]x = 4 - \sqrt{\frac{21}{2}}[/tex] and [tex]x = -4 + \sqrt{\frac{21}{2}}[/tex]

D. [tex]x = -4 - \sqrt{\frac{41}{2}}[/tex] and [tex]x = -4 + \sqrt{\frac{41}{2}}[/tex]



Answer :

To find the zeros of the quadratic function [tex]\( f(x) = 2x^2 + 16x - 9 \)[/tex], we need to solve the quadratic equation [tex]\( 2x^2 + 16x - 9 = 0 \)[/tex].

The general form of a quadratic equation is [tex]\( ax^2 + bx + c = 0 \)[/tex], where [tex]\( a = 2 \)[/tex], [tex]\( b = 16 \)[/tex], and [tex]\( c = -9 \)[/tex]. The solutions for this equation can be found using the quadratic formula:

[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

First, let's compute the discriminant [tex]\(\Delta\)[/tex]:

[tex]\[ \Delta = b^2 - 4ac \][/tex]

Substituting the values of [tex]\( a \)[/tex], [tex]\( b \)[/tex], and [tex]\( c \)[/tex]:

[tex]\[ \Delta = 16^2 - 4 \cdot 2 \cdot (-9) \][/tex]

[tex]\[ \Delta = 256 + 72 \][/tex]

[tex]\[ \Delta = 328 \][/tex]

Next, we calculate the square root of the discriminant [tex]\(\sqrt{\Delta}\)[/tex]:

[tex]\[ \sqrt{328} = 2 \sqrt{82} \][/tex]

Now, we substitute [tex]\(\Delta\)[/tex] back into the quadratic formula:

[tex]\[ x = \frac{-16 \pm 2\sqrt{82}}{4} \][/tex]

Simplifying:

[tex]\[ x = \frac{-16 \pm 2\sqrt{82}}{4} = \frac{-16 \pm \sqrt{82}}{2} \][/tex]

[tex]\[ x = -4 \pm \sqrt{\frac{41}{2}} \][/tex]

This means the solutions are:

[tex]\[ x_1 = -4 - \sqrt{\frac{41}{2}} \][/tex]
[tex]\[ x_2 = -4 + \sqrt{\frac{41}{2}} \][/tex]

Therefore, the correct pair of zeros for the quadratic function [tex]\( f(x) = 2x^2 + 16x - 9 \)[/tex] is:

[tex]\[ x = -4 - \sqrt{\frac{41}{2}} \quad \text{and} \quad x = -4 + \sqrt{\frac{41}{2}} \][/tex]

Hence, the correct choice is:
[tex]\[ x = -4 - \sqrt{\frac{41}{2}}, \quad x = -4 + \sqrt{\frac{41}{2}} \][/tex]