Multiply Conjugate, (4+5i)(4-5i), Help?

👨🏻‍🏫 學術台數學

[匿名]

2016-03-19 4:16 am

I'm getting 9-i, is that right?

回答 (4)

[匿名]

2016-03-19 4:24 am

( 4 + 5i )( 4 - 5i) = ( 4)^2 - ( 5i)^2 = 16 - 25 i^2 = 16 - 25 ( - 1 ) = 41

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[匿名]

2016-03-19 5:33 am

16 -25i² = 16+25 = 41 since i²= -1

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用戶55769

2016-03-19 4:34 am

(4 + 5i)(4 - 5i)
= 16 - 25i^2
= 41

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Sqdancefan

2016-03-19 4:29 am

The product of conjugate complex numbers is always completely real.
.. (4+5i)*(4-5i) = 4^2 - (5i)^2 = 16 - (-25) = 41

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