The request of the problem is vague since it is not clear what is needed, hence, supposing that you need to work with a fraction that has a complex number to dennominator, you need to perform first a multiplication to both, numerator and denominator, with the conjugate of the complex number, such that:
`1/(x + i*y) = (x - i*y)/((x + i*y)(x - i*y))`
You need to convert the product to denominator into a difference of squares, such that:
`1/(x + i*y) = (x - i*y)/(x^2 - y^2*i^2)`
`1/(x + i*y) = (x - i*y)/(x^2 - y^2*(-1))`
`1/(x + i*y) = (x - i*y)/(x^2 + y^2)`
Hence, when the fraction has a complex number to denominator, you need to multiply by its conjugate to transform the complex denominator into a real denomminator.