1. **Identify the roots of the polynomial P(z)=z2019−1:**
The roots of P(z) are the 2019th roots of unity, which can be written as:
zk=e20192kπifork=0,1,2,…,2018.
2. Express the roots in terms of real and imaginary parts:
Each root zk can be written as zk=xk+iyk, where:
xk=cos(20192kπ)andyk=sin(20192kπ).
3. **Form the new roots for the polynomial Q:**
The new roots are 2xk+iyk. Therefore, the new roots are:
2cos(20192kπ)+isin(20192kπ).
4. Express the new roots in exponential form:
The new roots can be written as:
2cos(20192kπ)+isin(20192kπ)=eiθkwhereθk=tan−1(2cos(20192kπ)sin(20192kπ)).
5. **Construct the polynomial Q(z):**
The polynomial Q(z) is the monic polynomial with roots 2xk+iyk. Therefore, Q(z) can be written as:
Q(z)=k=0∏2018(z−(2cos(20192kπ)+isin(20192kπ))).
6. **Evaluate Q(−2):**
To find Q(−2), we substitute z=−2 into the polynomial:
Q(−2)=k=0∏2018(−2−(2cos(20192kπ)+isin(20192kπ))).
7. Simplify the expression:
Notice that:
−2−(2cos(20192kπ)+isin(20192kπ))=−2−2cos(20192kπ)−isin(20192kπ).
This can be further simplified using properties of roots of unity and symmetry.
8. Final simplification:
Using the fact that the product of all roots of unity is 1, and considering the symmetry and periodicity of the roots, we can simplify the product to:
Q(−2)=22018−1−32019.
The final answer is 22018−1−32019.