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Câu hỏi: Tìm số phức $z$ thỏa mãn $(3+4i)z+1-2i=i$.
A. $\dfrac{9}{25}-\dfrac{13}{25}i$.
B. $\dfrac{9}{25}+\dfrac{13}{25}i$.
C. $-\dfrac{9}{25}+\dfrac{13}{25}i$.
D. $-\dfrac{9}{25}-\dfrac{13}{25}i$.
A. $\dfrac{9}{25}-\dfrac{13}{25}i$.
B. $\dfrac{9}{25}+\dfrac{13}{25}i$.
C. $-\dfrac{9}{25}+\dfrac{13}{25}i$.
D. $-\dfrac{9}{25}-\dfrac{13}{25}i$.
$(3+4i)z+1-2i=i\Leftrightarrow (3+4i)z=3i-1\Leftrightarrow z=\dfrac{3i-1}{3+4i}=\dfrac{9}{25}+\dfrac{13}{25}i$.
Đáp án B.