degree of 2 zeros: 1-2i

Question

anonymous · Answer

much easier than it looks
there is an easy way, and a really really easy way
lets do the easy way first

anonymous · Answer

okay

anonymous · Answer

work backwards, like solving a quadratic equation backwards 
$$x=1-2i$$ subtract $1$
$$x-1=2i$$ square both sides (carefully)
$$(x-1)^2=(2i)^2\
x^2-2x+1=-4$$ then add $4$ and finish with 
$$x^2-2x+5$$

anonymous · Answer

want to try the really really easy way?

anonymous · Answer

sure !

anonymous · Answer

it is really really easy but it requires memorizing something 
if the zero of a quadratic is $a+bi$ then the quadratic is 
$$x^2-2ax+(a^2+b^2)$$
you had $1+2i$ so the quadratic is 
$$x^2-2\times 1x+(1^2+2^2)=x^2-2x+5$$

anonymous · Answer

what about when it tell you .. degree 3 zeros -1 with a multiplicity of 3 ?

anonymous · Answer

is -1 a and 3 b ?