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Verify whether there is a result of multiplication of the complex numbers (-2i+5)(i+7)...

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andrzej | Student, College Freshman | eNoter

Posted May 7, 2011 at 6:11 PM via web

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Verify whether there is a result of multiplication of the complex numbers (-2i+5)(i+7) is a complex number.

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giorgiana1976 | College Teacher | Valedictorian

Posted May 7, 2011 at 6:15 PM (Answer #1)

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We'll remove the brackets, using FOIL method:

(-2i+5)(i+7) = -2i^2 - 14i + 5i + 35

We know that i^2 = -1

(-2i+5)(i+7) = 2 - 9i + 35

We'll combine real parts:

(-2i+5)(i+7) = 37 - 9i

The result of multiplication of the given complex numbers is also a complex number: 37 - 9i.

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