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 find the values of [tex]\( x \)[/tex] for which the function [tex]\( f(x) = 4|x - 5| + 3 \)[/tex] equals 15, we need to solve the equation:

[tex]\[ 4|x - 5| + 3 = 15 \][/tex]

Step 1: Subtract 3 from both sides.

Start by isolating the absolute value term:

[tex]\[ 4|x - 5| + 3 - 3 = 15 - 3 \][/tex]

Which simplifies to:

[tex]\[ 4|x - 5| = 12 \][/tex]

Step 2: Divide by 4.

Next, divide both sides of the equation by 4 to further isolate the absolute value:

[tex]\[ |x - 5| = \frac{12}{4} \][/tex]

This simplifies to:

[tex]\[ |x - 5| = 3 \][/tex]

Step 3: Solve the absolute value equation.

The equation [tex]\( |x - 5| = 3 \)[/tex] means that the expression inside the absolute value, [tex]\( x - 5 \)[/tex], can be either 3 or -3. So we have two cases to consider:

- Case 1: [tex]\( x - 5 = 3 \)[/tex]
- Case 2: [tex]\( x - 5 = -3 \)[/tex]

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

Add 5 to both sides:

[tex]\[ x = 3 + 5 \][/tex]

[tex]\[ x = 8 \][/tex]

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

Add 5 to both sides:

[tex]\[ x = -3 + 5 \][/tex]

[tex]\[ x = 2 \][/tex]

We have found two values for [tex]\( x \)[/tex] that satisfy the original equation: [tex]\( x = 8 \)[/tex] and [tex]\( x = 2 \)[/tex].

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