Answer:
The number is +1
Explanation:
we have
![y=-2(x+2)^2-1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/h8yobzu074f4dxd3mmaujfdla0k4ucf276.png)
This is the equation of a vertical parabola with vertex at point (-2,-1)
The function has no real zeros
we know that
If the number +1 is added to the equation on the right side
then
------->
![y=-2(x+2)^2](https://img.qammunity.org/2020/formulas/mathematics/middle-school/d49hjptlyr75bs38nhvjuoczho388wurth.png)
Is a translation one unit up
The vertex of the parabola will be the point (-2,0) and the function will have one real root
see the attached figure to better understand the problem