Under the section of complex number, i faced 2 questions which i couldn't answer... Here they go...

-Show that x=1-2i is a root of the equation x3-3x2+7x-5=0. Hence, find all the roots of the equation.

-Express Attachment 20803 in the form a+ib, where a>0

Note: for both question, 'i' represents imaginary number... Please show step-by-step working if possible... Thanks...