Math Problem Statement

What point on the parabola y = 8 - x^2 is closest to the point (8, 8)?

Solution

To solve this problem, we need to find the point on the parabola y=8x2y = 8 - x^2 that is closest to the point (8,8)(8, 8).

Solution Outline

  1. Define the Distance Function: The distance DD between any point (x,y)(x, y) on the parabola and the point (8,8)(8, 8) is given by: D=(x8)2+(y8)2D = \sqrt{(x - 8)^2 + (y - 8)^2} Since y=8x2y = 8 - x^2, substitute yy in terms of xx to express DD as a function of xx alone.

  2. Rewrite the Distance Squared: To simplify, minimize D2D^2 instead of DD, since the minimum of D2D^2 will occur at the same point as the minimum of DD. Thus, we define: D2=(x8)2+(8x28)2D^2 = (x - 8)^2 + (8 - x^2 - 8)^2 Simplifying, this becomes: D2=(x8)2+(x2)2D^2 = (x - 8)^2 + (-x^2)^2 D2=(x8)2+x4D^2 = (x - 8)^2 + x^4

  3. Differentiate and Find Critical Points: Differentiate D2D^2 with respect to xx, set the derivative equal to zero, and solve for xx to find the critical points.

  4. Evaluate and Determine the Closest Point: Calculate yy for the resulting xx-value(s) and determine which point gives the minimum distance.

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Math Problem Analysis

Mathematical Concepts

Algebra
Geometry
Optimization
Parabolas
Distance Formula

Formulas

Distance formula: D = sqrt((x2 - x1)^2 + (y2 - y1)^2)
Distance squared: D^2 = (x - 8)^2 + (y - 8)^2
Substitute y = 8 - x^2 into D^2

Theorems

Optimization using derivatives
Critical points of a function

Suitable Grade Level

Grades 10-12