Discrete Mathematics and Its Applications, Seventh Edition

Published by McGraw-Hill Education
ISBN 10: 0073383090
ISBN 13: 978-0-07338-309-5

Chapter 5 - Section 5.1 - Mathematical Induction - Exercises - Page 333: 79

Answer

By the inductive hypothesis we can fill each of these eight objects with tiles. Putting these tilings together produces the desired tiling.

Work Step by Step

--showing that a three-dimensional 2^n × 2^n × 2^n checkerboard with one 1 × 1 × 1 cube missing can be completely covered by 2 × 2 × 2 cubes with one 1 × 1 × 1 cube removed. --Let P(n) be the statement that every 2^n×2^n×2^n checkerboard with a 1 × 1 × 1 cube removed can be covered by tiles that are 2×2×2 cubes each with a 1×1×1 cube removed. -- The basic step, P(1), holds because one tile coincides with the solid to be tiled. Now assume that P(k) holds. Now consider a 2k+1×2k+1×2k+1 cube with a 1×1×1 cube removed. -Split this object into eight pieces using planes parallel to its faces and running through its center. The missing 1 × 1 × 1 piece occurs in one of these eight pieces. Now position one tile with its center at the center of the large object so that the missing 1 × 1 × 1 cube lies in the octant in which the large object is missing a 1×1×1 cube. -This creates eight 2k×2k×2k cubes, each missing a 1 × 1 × 1 cube. By the inductive hypothesis we can fill each of these eight objects with tiles. Putting these tilings together produces the desired tiling.
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