Understand that -(-a) = a for any number a. 0706.2.5

Links verified on 6/10/2014

1. How to Multiply Negatives - a lesson contributed to algebra.com
2. Multiplying (and Dividing) Negative Numbers - a lesson from Purple Math
3. Multiplying Negative by a Negative - two Dr. Math volunteers give answers and one of them even gives a good example of a real life situation
4. Multiplying Negative Numbers - a printable worksheet
5. Negative Times Negative is What? - this answer to a ninth grade student includes a grammatical analogy and a mathematical alanogy for understanding the concept
6. Negative x Negative = Positive - explanation from Dr. Math at the Math Forum
7. Why does multiplying two negative numbers make a positive? - Math is Fun uses a cute number line illustration to make the point