When should the plus/minus sign be used when dealing with square roots?

Click For Summary

Discussion Overview

The discussion revolves around the use of the plus/minus sign when dealing with square roots, particularly in the context of solving equations like x² = 9. Participants explore the implications of this notation, its conventions, and the underlying mathematical principles.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • Some participants argue that the plus/minus sign should be applied consistently when taking square roots, suggesting that it retains more information about potential solutions.
  • Others contend that the conventional rule states that √(x²) = x, which does not account for negative solutions unless explicitly stated.
  • A few participants propose that the expression x = ±3 is valid but raises questions about the interpretation of equality and the nature of the solutions.
  • Some contributions highlight that using ± can lead to confusion or contradictions in certain contexts, particularly when considering the implications of equality.
  • One participant emphasizes that the notation ± is an "abuse of notation" that simplifies the solution process but may not hold up under strict mathematical scrutiny.
  • Several participants mention that when solving x² = 9, one can derive multiple equivalent equations, leading to the same solutions of x = 3 and x = -3.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the proper use of the plus/minus sign. There are competing views on whether it should be applied universally when taking square roots and how it relates to the concept of equality in mathematical expressions.

Contextual Notes

Some participants note that the discussion is complicated by the conventions of mathematical notation and the varying interpretations of equality and solution uniqueness.

  • #31
Dr. Mirrage said:
So, then the only question I still have is when should I use the plus/minus sign?
When it makes things easier -- when it makes it easier for you to (correctly) solve a problem, when it makes it easier for you to explain something, and so forth.

If you don't find it makes things easier, then don't use it.
 

Similar threads

  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
1K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 18 ·
Replies
18
Views
5K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K