i imaginary i \rightarrow \text{imaginary} #2

Algebra Level 3

( 12 i 3 ) 5 + ( 12 i 5 ) 5 = ? \large (12 - i^3)^5 + (12 - i^5)^5 = ?


The answer is 463224.

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1 solution

Naren Bhandari
Oct 13, 2017

Given that ( 12 i 3 ) 5 + ( 12 i 5 ) 5 = ( 12 + i ) 5 + ( 12 I ) 5 = z 1 + w 1 (12-i^3)^5+(12-i^5)^5 = (12+i)^5+(12-I)^5 = z_1 + w_1

where z 1 = ( 12 + i ) 5 z_1 = (12+i)^5 and w 1 = ( 12 i ) 5 w_1 = (12-i)^5 .

Here z 1 = ( 12 + i ) 5 = ( ( 12 + i ) 2 ) 2 ( 12 + i ) = ( 143 + 24 i 2 ) 2 ( 12 + i ) = ( 19873 + 6864 i ) ( 12 + i ) = 231612 + 102241 i \begin{aligned} z_1 = (12+i)^5 & = ((12+i)^2)^2(12+i) \\ & = (143+24i^2)^2(12+i) \\ & = (19873 +6864i)(12+i) \\ & = 231612 + 102241i\end{aligned} .

Similarly w 1 = ( 12 i ) 5 = ( ( 12 i ) 2 ) 2 ( 12 i ) = ( 143 24 i 2 ) 2 ( 12 i ) = ( 19873 6864 i ) ( 12 i ) = 231612 102241 i \begin{aligned} w_1 = (12-i)^5 & = ((12-i)^2)^2(12-i) \\ & = (143-24i^2)^2(12-i) \\ & = (19873 -6864i)(12-i) \\ & = 231612 - 102241i\end{aligned} .

Therefore, z 1 + w 1 = 231612 + 10224 i + 23612 10224 i 463224 z_1+w_1 = 231612+10224i +23612-10224i \implies \boxed{463224}

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