Evaluate
-21-12i
Real Part
-21
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3i\left(-4\right)+3\times 7i^{2}
Multiply 3i times -4+7i.
3i\left(-4\right)+3\times 7\left(-1\right)
By definition, i^{2} is -1.
-21-12i
Do the multiplications. Reorder the terms.
Re(3i\left(-4\right)+3\times 7i^{2})
Multiply 3i times -4+7i.
Re(3i\left(-4\right)+3\times 7\left(-1\right))
By definition, i^{2} is -1.
Re(-21-12i)
Do the multiplications in 3i\left(-4\right)+3\times 7\left(-1\right). Reorder the terms.
-21
The real part of -21-12i is -21.
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