Solve (-2+3i)/(5-4i)

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

Evaluate

$$-\frac{22}{41}+\frac{7}{41}i\approx -0.536585366+0.170731707i$$

Solution Steps

Multiply both numerator and denominator by the complex conjugate of the denominator, 5+4i.

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

Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}.

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

By definition, i^{2} is -1. Calculate the denominator.

$$\frac{\left(-2+3i\right)\left(5+4i\right)}{41}$$

Multiply complex numbers -2+3i and 5+4i like you multiply binomials.

$$\frac{-2\times 5-2\times \left(4i\right)+3i\times 5+3\times 4i^{2}}{41}$$

By definition, i^{2} is -1.

$$\frac{-2\times 5-2\times \left(4i\right)+3i\times 5+3\times 4\left(-1\right)}{41}$$

Do the multiplications in -2\times 5-2\times \left(4i\right)+3i\times 5+3\times 4\left(-1\right).

$$\frac{-10-8i+15i-12}{41}$$

Combine the real and imaginary parts in -10-8i+15i-12.

$$\frac{-10-12+\left(-8+15\right)i}{41}$$

Do the additions in -10-12+\left(-8+15\right)i.

$$\frac{-22+7i}{41}$$

Divide -22+7i by 41 to get -\frac{22}{41}+\frac{7}{41}i.

$$-\frac{22}{41}+\frac{7}{41}i$$

Real Part

$$-\frac{22}{41} = -0.5365853658536586$$

Solution Steps

Multiply both numerator and denominator of \frac{-2+3i}{5-4i} by the complex conjugate of the denominator, 5+4i.

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

Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}.

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

By definition, i^{2} is -1. Calculate the denominator.

$$Re(\frac{\left(-2+3i\right)\left(5+4i\right)}{41})$$

Multiply complex numbers -2+3i and 5+4i like you multiply binomials.

$$Re(\frac{-2\times 5-2\times \left(4i\right)+3i\times 5+3\times 4i^{2}}{41})$$

By definition, i^{2} is -1.

$$Re(\frac{-2\times 5-2\times \left(4i\right)+3i\times 5+3\times 4\left(-1\right)}{41})$$

Do the multiplications in -2\times 5-2\times \left(4i\right)+3i\times 5+3\times 4\left(-1\right).

$$Re(\frac{-10-8i+15i-12}{41})$$

Combine the real and imaginary parts in -10-8i+15i-12.

$$Re(\frac{-10-12+\left(-8+15\right)i}{41})$$

Do the additions in -10-12+\left(-8+15\right)i.

$$Re(\frac{-22+7i}{41})$$

Divide -22+7i by 41 to get -\frac{22}{41}+\frac{7}{41}i.

$$Re(-\frac{22}{41}+\frac{7}{41}i)$$

The real part of -\frac{22}{41}+\frac{7}{41}i is -\frac{22}{41}.

$$-\frac{22}{41}$$