What is the value of b and c

Which of the following is the true for f(x) = 5cos

Write a polynomial function f of least degree that has rational coefficients, a leading coefficient of 1, and the given zeros. 3, 4+2i, 1+(sqrt)7 the answer is supposed to be: f(x)=x(^5)-13x(^4)+60x(^3)-82x(^2)-144x+360 what am i doing wrong?

Hi, can anyone show me how to do this problem? 100 points for this. in advance