zeros of function

in order to find the zeros of  function, we can use long divition and find the complete factorization. We use the given fator to find the complte factorization. fist we have to test weather or not the given number is a factor. After we find the complete factorization, we can use the quadratic formula to find the zeros. If the answer involves with a negative square root, we have to use imagery numbers to express the answer. I think the problems with the imagery numbers are hard for me, it is really easy to make mistakes during the calculations. I did not understand the problems which they give you multiplicities and zeros, and ask me to find the function.