Answer: 
Step-by-step explanation:
To find the solutions of the quadratic equation given in the problem, you can apply the proccedure shown below:
- Subtract 40 from both sides of the equation.
- Multiply both sides of the equation by -1
- Apply square root to both sides of the equation.
Therefore, by applyin the steps above, you obtain:

The pythagorean theorem is more apt for the problem
For this problem, we are given a quadratic equation that models the total amount spent on clothing and footwear in the years 2000-2009. We need to use the model to determine the maximum amount spent during the period.
The equation is shown below:

Since the leading term is negative, the vertex of this function will represent an absolute maximum value. Therefore we can determine the vertex to answer the problem, the vertex's coordinates are given below:

Then we have:

In the year 2008, 384 billion was spent on clothing and footwear.