If a 3 − 3 a b 2 = 1 8 1 8 and b 3 − 3 a 2 b = 2 2 2 2 find the value of a 2 + b 2 .
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Ughhhh, I hit view explanation by mistake!
Slightly motivated but similar solution as @Culver Kwan 's solution:
Note that ( a − i b ) 3 = a 3 − 3 a b 2 + i ( b 3 − 3 a b 2 ) and similarly ( a + i b ) 3 = a 3 − 3 a b 2 − i ( b 3 − 3 a b 2 )
Now multiplying both of the above equation yields ( a 2 + b 2 ) 3 = ( a 3 − 3 a b 2 ) 2 + ( b 3 − 3 a 2 b ) 2 .
Hence the answer is ( 1 8 1 8 2 + 2 2 2 2 2 ) 1 / 3 = 2 0 2 .
Note: i = − 1 denotes the imaginary unit.
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( a 2 + b 2 ) 3 = ( a 3 − 3 a b 2 ) 2 + ( b 3 − 3 a 2 b ) 2 = 1 8 1 8 2 + 2 2 2 2 2 So a 2 + b 2 = 3 8 2 4 2 4 0 8 = 2 0 2