y=-x²+12
This is a parabola opening downward because the coefficient of x² =1 >0
The domain (the value of the input of x) is all real numbers.
to find some points (& you can extend to 1,000,000 points) that are on the graph, replace x by any value & you'll find the related value of y
Example:
f(1)= 1²+12 = 13 ==> for x=1 y=13 & this points ∈ to the parabolas
f(2) = 2²+12 =16 ===> for x=2, y=16) this points ∈ to the parabolas
and so on & so forth