roots of polynomial equations (complex #s)

so im just starting to learn about roots of polynomial equations with roots that are complex numbers and i dont understand them at all.. i hope you can help

A. Use the quadratic formula to find the roots of the equation x^2+4x+5=0. Simplify and compare the roots. what do you notice?

B. write a quadratic equation with integral coefficients such that one of its roots is 4-5i

C. Write a quartic equation with integral coefficients and with roots 7i and -3i

.....

so for A i think its x= -2+i and x=-2-i but i dont "notice" anything and have no idea how to do the other questions.

im thinking its something simple and im going to feel stupid once i find out the answer -.-