Question 1023391
Not full answers but only guidance:


1:
Just form the composition and simplify; and then let x=1 and evaluate.
Start as  {{{f(g(x))=5(x-2)^2-6}}}.



2:
Evaluate P when x=600.  You could find max profit by using general solution formula, and take the x value in the exact middle of the roots.  That will give the maximum P.  You could instead try to change P into its standard form but that may be more work than just using the formula for general solution and finding the middle value of x.  You can also choose to find a general transformation from general form to standard form, and then use that itself as a kind of formula.  That is,  {{{P=ax^2+bx+c}}} to start; and use Completing The Square to put this into standard form.  You can read the vertex directly from the standard form expression.