1.

Express `(2 + 3i)^(3)` in the form `(a + ib).`

Answer» We know that `(z_(1) + z_(2))^(3) = z_(1)^(3) + z_(2)^(3) + 3z_(1)z_(2)(z_(1)+z_(2))`.
`therefore" "(2+3i)^(3) = 2^(3)+(3i)^(3) + 3 xx 2 xx 3i xx (2 + 3i)`
`= 8 + 27i^(3)+36i+54i^(2)`
`= (8 - 27i + 36i - 54)" "[because i^(3) = -i and i^(2) = -1]`
`= (-46 + 9i)`.
Hence, `(2+3i)^(3) = (-46 + 9i)`.


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