Evaluate
3+9i
Real Part
3
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3i\times 3+3\left(-1\right)i^{2}
Multiply 3i times 3-i.
3i\times 3+3\left(-1\right)\left(-1\right)
By definition, i^{2} is -1.
3+9i
Do the multiplications. Reorder the terms.
Re(3i\times 3+3\left(-1\right)i^{2})
Multiply 3i times 3-i.
Re(3i\times 3+3\left(-1\right)\left(-1\right))
By definition, i^{2} is -1.
Re(3+9i)
Do the multiplications in 3i\times 3+3\left(-1\right)\left(-1\right). Reorder the terms.
3
The real part of 3+9i is 3.
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