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Which function has two [tex]$x$[/tex]-intercepts, one at [tex]$(0,0)$[/tex] and one at [tex]$(4,0)$[/tex]?

A. [tex]$f(x)=x(x-4)$[/tex]
B. [tex]$f(x)=x(x+4)$[/tex]
C. [tex]$f(x)=(x-4)(x-4)$[/tex]
D. [tex]$f(x)=(x+4)(x+4)$[/tex]

Sagot :

Certainly! Let's analyze each function one by one to determine which one meets the criteria of having [tex]$x$[/tex]-intercepts at [tex]$(0,0)$[/tex] and [tex]$(4,0)$[/tex]. The [tex]$x$[/tex]-intercepts of a function are the points where the function crosses the [tex]$x$[/tex]-axis, which occurs where [tex]$f(x) = 0$[/tex].

1. \( f(x) = x(x - 4) \)

For the function \( f(x) = x(x - 4) \), we set the function equal to zero to find the [tex]$x$[/tex]-intercepts:
[tex]\[ x(x - 4) = 0 \][/tex]
This equation holds when either \( x = 0 \) or \( x - 4 = 0 \). Solving \( x - 4 = 0 \), we get:
[tex]\[ x = 4 \][/tex]
So, the intercepts are at \( (0,0) \) and \( (4,0) \).

2. \( f(x) = x(x+4) \)

For the function \( f(x) = x(x + 4) \), we set the function equal to zero to find the [tex]$x$[/tex]-intercepts:
[tex]\[ x(x + 4) = 0 \][/tex]
This equation holds when either \( x = 0 \) or \( x + 4 = 0 \). Solving \( x + 4 = 0 \), we get:
[tex]\[ x = -4 \][/tex]
So, the intercepts are at \( (0,0) \) and \( (-4,0) \).

3. \( f(x) = (x - 4)(x - 4) \)

For the function \( f(x) = (x - 4)(x - 4) \), we set the function equal to zero to find the [tex]$x$[/tex]-intercepts:
[tex]\[ (x - 4)(x - 4) = 0 \][/tex]
This equation holds when \( x - 4 = 0 \). Solving \( x - 4 = 0 \), we get:
[tex]\[ x = 4 \][/tex]
This gives a repeated intercept at \( (4,0) \).

4. \( f(x) = (x + 4)(x + 4) \)

For the function \( f(x) = (x + 4)(x + 4) \), we set the function equal to zero to find the [tex]$x$[/tex]-intercepts:
[tex]\[ (x + 4)(x + 4) = 0 \][/tex]
This equation holds when \( x + 4 = 0 \). Solving \( x + 4 = 0 \), we get:
[tex]\[ x = -4 \][/tex]
This gives a repeated intercept at \( (-4,0) \).

After analyzing each function, we see that the function \( f(x) = x(x - 4) \) has the [tex]$x$[/tex]-intercepts at [tex]$(0,0)$[/tex] and [tex]$(4,0)$[/tex]. Therefore, the correct function is:

[tex]\[ \boxed{1} \][/tex]