Write out in polar form all solutions to the the equation $(x^3 +8)(x^4 −i+1)=0$.
I saw another person asked the same question, but I would like someone to explain to me the $(x^4-i+1)$ part. I do not understand why we would factor out a $\sqrt2$, or how the cos and sin functions get a theta of $3\pi/4$.
I attached a picture of the solution to help.
Thank you.