The additive identity is 0 because adding 0 to any whole number leaves its value unchanged, and the multiplicative identity is 1 because multiplying any whole number by 1 leaves its value unchanged: and . This understanding supports simplifying numerical expressions and distinguishes multiplication by 1 from multiplication by 0; at this level, it is limited to whole-number addition and multiplication, not identities for other operations or abstract algebraic systems.
An identity is a number that leaves another number unchanged when you use it in an operation.
Simplify:
Step 1: Use the multiplicative identity.
Since multiplying by does not change a number,
The expression becomes:
Step 2: Use the additive identity.
Since adding does not change a number,
Now the expression is:
So,
Remember: adding keeps a number the same, and multiplying by keeps a number the same. Multiplying by is different because it makes the product .
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