Question 240795
You know that roots result in zeros. 
So a zero at x=-2 means (x+2) is a factor in the formula for the polynomial.
Likewise you are told you have an imaginary root at 7i. You know that imaginary roots come in pairs (7i , -7i)
So two more factors are (x-7i) and (x+7i)
Now you have three terms. The polynomial is the product of those three factors.
{{{p(y) = (x+2)(x+7i)(x-7i)}}}
{{{p(y) = (x+2)(x^2-49i^2)}}}
{{{p(y) = (x+2)(x^2+49)}}}
All you need to do now is simplify by multiplying it all out. I'll leave that to you, because I know you can do that. Ping me if you need more help