Tính $\Large z=\dfrac{2+3i}{4-5i}$. $\Large -\dfrac{3}{43}+\dfrac{23}{

Tính $\Large z=\dfrac{2+3i}{4-5i}$.

• A.

  $\Large -\dfrac{3}{43}+\dfrac{23}{43}i$.

• B.

  $\Large -\dfrac{7}{41}+\dfrac{22}{41}i$.

• C.

  $\Large \dfrac{3}{43}+\dfrac{23}{43}i$.

• D.

  $\Large \dfrac{7}{41}+\dfrac{22}{41}i$.

Chọn B
Ta có $\Large z=\dfrac{2+3i}{4-5i}=\dfrac{(2+3i)(4+5i)}{4^2+5^2}=-\dfrac{7}{41}+\dfrac{22}{41}i$.