Question

For the graph below, what should the domain be so that the function is at least 600? (1 point)

Answer 1

Answer: The first interval:0 ≤ x ≤ 20

Procedure

You have to solve this inequality

-2x^2 +40x +600 ≥ 600

-2x^2 +40x  ≥ 0

-x^2+20x ≥ 0

x^2 - 20 x ≤ 0

x(x-20) ≤ 0

That is only possible if the two factors have different signs.

Let's examine the possibilities

       x ≥ 0 and x -20 ≤ 0⇔x≤20, that is 0≤x≤20

The other possibility is

       x ≤ 0 and x - 20 ≥ 0 ⇔x≥20. This conditions is not possible.

So the solution is 0≤x≤20