Question

Difficulty: HardReal Numbers, Number Line, and Absolute Value

On the real number line, points PP, QQ, and RR have coordinates xx, yy, and zz, respectively, such that x2=5|x - 2| = 5, y+4=3|y + 4| = 3, and zz is the midpoint of segment PQPQ. If x<yx < y, what is the value of zz?

Answer: -2

Answer

The coordinate of point RR (the value of zz) is 2-2.
Solving the two absolute value equations yields x{3,7}x \in \{-3, 7\} and y{7,1}y \in \{-7, -1\}. Testing the given constraint x<yx < y across all four possible ordered pairs reveals that only x=3x = -3 and y=1y = -1 satisfy the condition, since 3<1-3 < -1 is true while all other pairs fail. The midpoint of points with coordinates 3-3 and 1-1 is 3+(1)2=2\frac{-3 + (-1)}{2} = -2.

Step-by-Step Solution

1
Solve the absolute value equation x2=5|x - 2| = 5.
x=7x = 7 or x=3x = -3
The equation x2=5|x - 2| = 5 splits into x2=5    x=7x - 2 = 5 \implies x = 7 and x2=5    x=3x - 2 = -5 \implies x = -3.
2
Solve the absolute value equation y+4=3|y + 4| = 3.
y=1y = -1 or y=7y = -7
The equation y+4=3|y + 4| = 3 splits into y+4=3    y=1y + 4 = 3 \implies y = -1 and y+4=3    y=7y + 4 = -3 \implies y = -7.
3
Evaluate all candidate pairs (x,y)(x, y) under the inequality constraint x<yx < y.
The only valid pair is x=3x = -3 and y=1y = -1.
Comparing all four combinations: 7<17 < -1 (false), 7<77 < -7 (false), 3<7-3 < -7 (false), and 3<1-3 < -1 (true).
4
Calculate the midpoint zz of the segment PQPQ.
z=2z = -2
The midpoint of coordinates 3-3 and 1-1 on a number line is given by their average: 3+(1)2=2\frac{-3 + (-1)}{2} = -2.

Key Concept

Absolute Value Equations and Midpoint on the Real Number Line
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