SOLUTION: How would you go about finding when the percent of foreign �born citizen was at its highest and when it was at its lowest percent since 1990? The U.S. population that was foreig

Question 1036215: How would you go about finding when the percent of foreign �born citizen was at its highest and when it was at its lowest percent since 1990?
The U.S. population that was foreign-born since 1900 can be modeled by where t = 0 in 1990.
Here is the graph of the polynomial function: http://postimg.org/image/hz7mo786z/
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
where t = 0 in 1990.
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Find the 1st derivative.
P'(t) =
---
Solve the quadratic for t, the times of local max and min.

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=0.00016 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 74.0253073352042, 3.75247044257356. Here's your graph:

==========
t = x + 1900
--> 1903 & 1974
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You can see on the graph the 1903 is the max and 1974 is the minimum.
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To determine whether it's a max or min, find the 2nd derivative of P(t)
---
P"(t) =
P"(3) = = -0.01292
< 0 --> maximum
---
P"(74) = 0.01264
> 0 --> minimum
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