Løs 3/4left(2-5iright)+1/2left(3+1/2iright)

$$\frac{ 3 }{ 4 } \left( 2-5i \right) + \frac{ 1 }{ 2 } \left( 3+ \frac{ 1 }{ 2 } i \right)$$

Evaluer

$$3-\frac{7}{2}i=3-3,5i$$

Løsningsvejledning

Multiplicer \frac{3}{4} gange 2-5i.

$$\frac{3}{4}\times 2+\frac{3}{4}\times \left(-5i\right)+\frac{1}{2}\left(3+\frac{1}{2}i\right)$$

Lav multiplikationerne i \frac{3}{4}\times 2+\frac{3}{4}\times \left(-5i\right).

$$\frac{3}{2}-\frac{15}{4}i+\frac{1}{2}\left(3+\frac{1}{2}i\right)$$

Multiplicer \frac{1}{2} gange 3+\frac{1}{2}i.

$$\frac{3}{2}-\frac{15}{4}i+\frac{1}{2}\times 3+\frac{1}{2}\times \left(\frac{1}{2}i\right)$$

Lav multiplikationerne i \frac{1}{2}\times 3+\frac{1}{2}\times \left(\frac{1}{2}i\right).

$$\frac{3}{2}-\frac{15}{4}i+\left(\frac{3}{2}+\frac{1}{4}i\right)$$

Kombiner de reelle og imaginære dele.

$$\frac{3}{2}+\frac{3}{2}+\left(-\frac{15}{4}+\frac{1}{4}\right)i$$

Lav additionerne.

$$3-\frac{7}{2}i$$

Reel del

$$3$$

Løsningsvejledning

Multiplicer \frac{3}{4} gange 2-5i.

$$Re(\frac{3}{4}\times 2+\frac{3}{4}\times \left(-5i\right)+\frac{1}{2}\left(3+\frac{1}{2}i\right))$$

Lav multiplikationerne i \frac{3}{4}\times 2+\frac{3}{4}\times \left(-5i\right).

$$Re(\frac{3}{2}-\frac{15}{4}i+\frac{1}{2}\left(3+\frac{1}{2}i\right))$$

Multiplicer \frac{1}{2} gange 3+\frac{1}{2}i.

$$Re(\frac{3}{2}-\frac{15}{4}i+\frac{1}{2}\times 3+\frac{1}{2}\times \left(\frac{1}{2}i\right))$$

Lav multiplikationerne i \frac{1}{2}\times 3+\frac{1}{2}\times \left(\frac{1}{2}i\right).

$$Re(\frac{3}{2}-\frac{15}{4}i+\left(\frac{3}{2}+\frac{1}{4}i\right))$$

Kombiner de reelle og imaginære dele i \frac{3}{2}-\frac{15}{4}i+\frac{3}{2}+\frac{1}{4}i.

$$Re(\frac{3}{2}+\frac{3}{2}+\left(-\frac{15}{4}+\frac{1}{4}\right)i)$$

Lav additionerne i \frac{3}{2}+\frac{3}{2}+\left(-\frac{15}{4}+\frac{1}{4}\right)i.

$$Re(3-\frac{7}{2}i)$$

Den reelle del af 3-\frac{7}{2}i er 3.

$$3$$