Elementary Linear Algebra 7th Edition

Published by Cengage Learning
ISBN 10: 1-13311-087-8
ISBN 13: 978-1-13311-087-3

Appendix - Mathematical Induction and Other Forms of Proofs - Exercises - Page A6: 17

Answer

See below.

Work Step by Step

Assume the statement is false. Then $a\ne0$ and $b\ne0$. But then $(a+b)^2=a^2+b^2+2ab$ in which $2ab\ne0$, thus $(a+b)^2\ne a^2+b^2$, but this is a contradiction. Thus the statement is true.
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