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Lorico [155]
3 years ago
11

What is the value of (7 + 2i)(3 - i)?

Mathematics
1 answer:
Harrizon [31]3 years ago
7 0
There are two ways to work this out: normal variables or using "imaginary" numbers.

Normal variables:
(7+2i)(3-i)\\(7*3)+[7*(-i)]+(3*2i)+[2i*(-i)]\\21-7i+6i-2i^{2}\\\\21-i-2i^{2}

Imaginary numbers:
Using the result from earlier:
21-i-2i^{2}
Now since i = \sqrt{-1}, then the expression becomes:
21-i-2i^{2}\\21-i-2(\sqrt{-1})^{2}\\21-i+(-2)(-1)\\21-i+2\\\\23-i
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