Question

Difficulty: MediumLoci and Geometric Constructions

A point P(x,y)P(x, y) moves in the Cartesian plane such that it is always equidistant from the two fixed points A(2,1)A(2, 1) and B(6,5)B(6, 5). If the locus of PP intersects the line 2x+y=142x + y = 14 at the point (x0,y0)(x_0, y_0), what is the value of x0x_0?

Answer: 7

Answer

The value of x0x_0 is 77.
The locus of points equidistant from A(2,1)A(2, 1) and B(6,5)B(6, 5) is the perpendicular bisector of line segment ABAB. The midpoint of ABAB is (4,3)(4, 3) and its slope is 11, giving the perpendicular bisector a slope of 1-1. The equation of this locus is y3=1(x4)y - 3 = -1(x - 4), or x+y=7x + y = 7. Subtracting x+y=7x + y = 7 from 2x+y=142x + y = 14 directly gives x0=7x_0 = 7.

Step-by-Step Solution

1
Determine the equation of the locus of point P
The locus of P is the perpendicular bisector of segment AB, represented by x+y=7x + y = 7.
The set of all points equidistant from two fixed points forms the perpendicular bisector of the line segment connecting those points.
2
Find the point of intersection with the line 2x+y=142x + y = 14
Solving x+y=7x + y = 7 and 2x+y=142x + y = 14 simultaneously gives x0=7x_0 = 7.
The intersection point of two geometric lines must satisfy both equations simultaneously.

Key Concept

Perpendicular Bisector Locus and Line Intersections
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