High School

Given the function [tex]f(x)=4|x-5|+3[/tex], for what values of [tex]x[/tex] is [tex]f(x)=15[/tex]?

A. [tex]x=2, x=8[/tex]
B. [tex]x=1.5, x=8[/tex]
C. [tex]x=2, x=7.5[/tex]
D. [tex]x=0.5, x=7.5[/tex]

Answer :

To solve the problem, we need to find the values of [tex]\( x \)[/tex] for which the function [tex]\( f(x) = 4|x-5| + 3 \)[/tex] equals 15. Let's walk through the solution step by step:

1. Set the function equal to 15:
We have the equation:
[tex]\[
4|x-5| + 3 = 15
\][/tex]

2. Isolate the absolute value expression:
Subtract 3 from both sides to get:
[tex]\[
4|x-5| = 12
\][/tex]

3. Simplify the equation:
Divide both sides by 4:
[tex]\[
|x-5| = 3
\][/tex]

4. Solve the absolute value equation:
The absolute value equation [tex]\( |x-5| = 3 \)[/tex] can be broken into two separate cases because the absolute value of a number represents its distance from zero on the number line.

- Case 1: [tex]\( x - 5 = 3 \)[/tex]
Solve for [tex]\( x \)[/tex]:
[tex]\[
x = 3 + 5 = 8
\][/tex]

- Case 2: [tex]\( x - 5 = -3 \)[/tex]
Solve for [tex]\( x \)[/tex]:
[tex]\[
x = -3 + 5 = 2
\][/tex]

5. Conclusion:
The values of [tex]\( x \)[/tex] for which [tex]\( f(x) = 15 \)[/tex] are [tex]\( x = 8 \)[/tex] and [tex]\( x = 2 \)[/tex].

Therefore, the correct answer is [tex]\( x = 2, x = 8 \)[/tex].