Complex addition is closed: Sum or difference of two complex numbers is another complex number.

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What does 'closure' mean?

- closed
- not open
- both the above
- both the above

Answer is 'both the above'

What is the "span" mean?

- Full extent of something; all that is included in that;
- Full extent of something; all that is included in that;
- past tense of spin

The answer is 'Full extent of something'

What is the span of complex numbers?

- `a+ib` with `a,b in RR`
- real and imaginary parts taking any real number
- both the above
- both the above

The answer is 'Both the above'

The span of complex numbers or the set of complex numbers is represented as `CC`.

When any two complex numbers are added will it result in a number within the span of complex numbers?

- Yes. It will be another complex number.
- Yes. It will be another complex number.
- No. It extends the complex numbers to something beyond the set of complex numbers.

The answer is 'Yes. It will be another complex number'

• Sum or difference of two complex numbers is another complex number - closure property

**Closure Property of Addition and Subtraction: **For any given complex numbers `z_1, z_2 in CC`, ` z_1 +- z_2 in CC`.

*Solved Exercise Problem: *

Given a complex number `z` and `a`. What will be the sum `z+a`?

- a real number
- a complex number
- a complex number
- addition between a complex number and real number is not defined

The answer is 'a complex number'

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