A fraction has a denominator of 2 + 7i. What is multiplied with the fraction to rationalize the fraction?

options
2 + 7i

7 + 2i

2 – 7i

7 – 2i s

Question

A fraction has a denominator of 2 + 7i. What is multiplied with the fraction to rationalize the fraction? 

options
2 + 7i

7 + 2i

2 – 7i

7 – 2i s

anonymous · Answer

It's conjugate. (2 - 7i)

anonymous · Answer

Right. Don't be intimidated by the term, but (2-7i) is what is called the "complex conjugate." It just means that the real part (the part without i) is the same, and the imaginary part (the part with i in it) has changed signs.

anonymous · Answer

And the reason for that is that if you FOIL those two things, the two middle terms cancel each other and you get just a real number =D