Which function has real zeros at [tex]$x=-10$[/tex] and [tex][tex]$x=-6$[/tex][/tex]?

A. [tex]f(x)=x^2+16x+60[/tex]

B. [tex]f(x)=x^2-16x+60[/tex]

C. [tex]f(x)=x^2+4x+60[/tex]

D. [tex]f(x)=x^2-4x+60[/tex]



Answer :

To determine which function has real zeros at [tex]\( x = -10 \)[/tex] and [tex]\( x = -6 \)[/tex], we need to evaluate each of the given functions by finding their roots. The roots of a quadratic equation [tex]\( ax^2 + bx + c = 0 \)[/tex] are found using the quadratic formula:

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

Let's examine each function:

1. Function [tex]\( f(x) = x^2 + 16x + 60 \)[/tex]:
[tex]\[ x = \frac{{-16 \pm \sqrt{{16^2 - 4 \cdot 1 \cdot 60}}}}{2 \cdot 1} = \frac{{-16 \pm \sqrt{{256 - 240}}}}{2} = \frac{{-16 \pm \sqrt{16}}}{2} = \frac{{-16 \pm 4}}{2} \][/tex]
[tex]\[ x = \frac{{-16 + 4}}{2} = -6 \quad \text{or} \quad x = \frac{{-16 - 4}}{2} = -10 \][/tex]

The roots are [tex]\( x = -10 \)[/tex] and [tex]\( x = -6 \)[/tex].

2. Function [tex]\( f(x) = x^2 - 16x + 60 \)[/tex]:
[tex]\[ x = \frac{{16 \pm \sqrt{{(-16)^2 - 4 \cdot 1 \cdot 60}}}}{2 \cdot 1} = \frac{{16 \pm \sqrt{{256 - 240}}}}{2} = \frac{{16 \pm \sqrt{16}}}{2} = \frac{{16 \pm 4}}{2} \][/tex]
[tex]\[ x = \frac{{16 + 4}}{2} = 10 \quad \text{or} \quad x = \frac{{16 - 4}}{2} = 6 \][/tex]

The roots are [tex]\( x = 10 \)[/tex] and [tex]\( x = 6 \)[/tex].

3. Function [tex]\( f(x) = x^2 + 4x + 60 \)[/tex]:
[tex]\[ x = \frac{{-4 \pm \sqrt{{4^2 - 4 \cdot 1 \cdot 60}}}}{2 \cdot 1} = \frac{{-4 \pm \sqrt{{16 - 240}}}}{2} = \frac{{-4 \pm \sqrt{-224}}}{2} \][/tex]

The discriminant is negative ([tex]\(16 - 240 = -224\)[/tex]), thus the equation has no real roots.

4. Function [tex]\( f(x) = x^2 - 4x + 60 \)[/tex]:
[tex]\[ x = \frac{{4 \pm \sqrt{{(-4)^2 - 4 \cdot 1 \cdot 60}}}}{2 \cdot 1} = \frac{{4 \pm \sqrt{{16 - 240}}}}{2} = \frac{{4 \pm \sqrt{-224}}}{2} \][/tex]

The discriminant is negative ([tex]\(16 - 240 = -224\)[/tex]), thus the equation has no real roots.

Comparing the results, we see that the function [tex]\( f(x) = x^2 + 16x + 60 \)[/tex] is the one that has real zeros at [tex]\( x = -10 \)[/tex] and [tex]\( x = -6 \)[/tex].

Therefore, the function with real zeros at [tex]\( x = -10 \)[/tex] and [tex]\( x = -6 \)[/tex] is:

[tex]\[ f(x) = x^2 + 16x + 60 \][/tex]