The function R(x) = -0.0065x² +0.23x + 8.47 models the American marriage rate R (the number of marriages per 100 population) x years after 1960. Based on this function, in what
year was the marriage rate the highest? (Hint: The vertex of a parabola is the maximum or
minimum.)
please help

Given:

The American marriage rate R,  x years after 1960 is defined by the function

To find:

The year in which the marriage rate is the highest.

Solution:

We have,

It is a quadratic function with negative leading coefficient. So, it is a downward parabola and vertex of downward parabola is maximum.

If a quadratic function is , then

In the given function,

Now, x-coordinate of vertex is

It means the marriage rate is highest after 17 years of 1960.

Therefore, the marriage rate is highest in year 1977.

there were only 2 presidents that were under the age of 45. theodore roosevelt, and jfk, that makes 5%