i have this question in calculus which i don't understand fully. My teacher is not replying and i have around 3 hours to solve this, so i'm gonna ask here and hope for someone to help me.
the exercises says: let $d = -3+4i.$
show that the number $u = 1+2i$ is the square root for d, $(u^2=d)$
i do not really understand what the problem is, could someone please explain? no need to give me the answer right away, but to explain the problem here.