Số \(\frac{1}{{1 + i}}\) bằng
(A) \(1+i\)
(B) \(\frac{1}{2}\left( {1 - i} \right)\)
(C) \(1–i\)
(D) \(i\)
\(\frac{1}{{1 + i}} = \frac{{1 - i}}{{1 - {i^2}}} = \frac{1}{2}\left( {1 - i} \right)\)
Chọn (B).
-- Mod Toán 12
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