Question 418430
If 5 + 2i is a zero, then 5 - 2i must also be a zero.  Let r be the third zero.

Then from algebra, the sum of the roots of the polynomial taken one at a time is equal to {{{-(-7)/1 = 7}}}, so that r + (5 + 2i) + (5 - 2i) = 7, or r + 10 = 7, or r = -3.  Therefore the zeros of the polynomial are -3,  5 + 2i, and  5 - 2i.