Year 9: Addition and subtraction of negative numbers

This cheat sheet covers addition and subtraction of negative numbers. Understanding this is crucial for many areas of maths and real-world applications.

Key Concepts

• Negative Numbers as Debt: Think of negative numbers as owing money or being in a debt.
• Adding Negative Numbers: Adding two negative numbers combines their negativity. For example, -3 + (-5) = -8
• Subtracting Negative Numbers: Subtracting a negative number is the same as adding a positive number. For example, 5 - (-2) = 5 + 2 = 7
• Subtracting Positive Numbers from Negative Numbers: This involves borrowing from the next higher place value.

Rules & Examples

• -a + b = b - a (Adding negative numbers)
• -a - b = -(a + b) (Equivalent to subtracting a negative)
• Example 1: -7 + (-2) = -9
• Example 2: 3 - (-4) = 3 + 4 = 7
• Example 3: -6 - (-1) = -6 + 1 = -5

Tips

• Visual Representation: Use a number line to help visualise addition and subtraction of negative numbers.
• Always simplify: Before performing calculations, simplify expressions involving negative numbers.