7.
$$f ( z ) = z ^ { 4 } + 4 z ^ { 3 } + 6 z ^ { 2 } + 4 z + a$$
where \(a\) is a real constant.
Given that \(1 + 2 \mathrm { i }\) is a complex root of the equation \(\mathrm { f } ( \mathrm { z } ) = 0\)
- write down another complex root of this equation.
- Hence, find the other roots of the equation \(\mathrm { f } ( \mathrm { z } ) = 0\)
- State the value of \(a\).
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