The daily electricity bill of a car manufacturing company can be modeled by the function C(x) = 800 – 10x + 0.25x^2, where C is the daily electricity bill, and x is the number of cars made each day.

How many cars should the company make to pay the lowest amount for electricity?

~Got the vertex which is (20,700) axis of symmetry is 20 now what do i do next to find the lowest amount of energy? do i find the zeros?

You already have the answer

minimum cost is at the vertex
x = 20 cars and C = 700 dollars

this is a parabola, its vertex is at the bottom,