How do i remove imaginary numbers from denominators?

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I am calculating towards getting the value of an unknown variable B. I got stuck when i came to the point where i have B = 1 divided on a complex number. I guess its the correct way to show this as a whole complex number and not as a dividation

$$ 1=B(0.25-0.25i) $$

$$B=\frac{1}{0.25-0.25i} $$

How can i easily get further on the part of putting B on the form B = 4+5i - numbers just an example.

(feel free to edit post if i write mathematical names wrong)

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When you have an imaginary number in the denominator, multiply the numerator and denominator by the conjugate of the denominator.

For example, given $a +bi, \,$ its conjugate is $a-bi$.

In your case the conjugate of the denominator is $0.25 + 0.25i$. So $$\begin{align} B=\frac{1}{0.25-0.25i}& =\frac{1}{0.25-0.25i}\cdot\dfrac{0.25 + 0.25i}{0.25 + 0.25i}\\ \\ & = \dfrac{0.25 + 0.25i}{\frac 1{16} + \frac 1{16}} \\ \\ & = \dfrac{\frac 14(1+i)}{\frac 1{8}} \\ \\ &= 2(1+i)\end{align}$$