During a storm, two teams of scientist leave a university at the same time in vans to search for tornadoes. The first team trave
ls east at 20 miles per hour and the second travels west at 25 mph. If their radios have a range of up to 90 miles, how long will it be before they lose radio contact?
If -3+5i is a solution, then by the conjugate root theorem, -3-5i is also a solution. We find the polynomial by multiplying together the factors. If x = -4, then x + 4 is the factor. If x = -3+5i, then (x-(-3+5i)) is a factor, and so is (x-(-3-5i)). Simplifying those down gives us as the first factor as (x+3-5i) and the second as (x+3+5i). We can FOIL those 2 together to get their product, and then FOIL in x+4. FOILing the 2 complex factors together gives us . If we combine like terms and cross out things that cancel it's much easier than what it looks like there! It simplifies down to . Since i^2 = -1, it simplifies further to and finally, to . Now we will FOIL in x+4. . Our final simplified third degree polynomial is