see question below

Question

The difference,d, in median earnings, in $1000s, between high school graduates and college graduates can be approximated by d= -0.002 x2 + .319x + 7.512, where x is the number of years after 1965. Based on this model, estimate to the nearest year when the difference in median earnings was $15,000

Answer 1

Set d=15.

 

-0.002x² + 0.319x + 7.512 = 15

 

-0.002x² + 0.319x - 7.488 = 0

 

 

Use the quadratic formula to solve for x.  You will get two x values.  Accept the positive value of x.  Round the positive of x to the nearest integer.

 

Year = x + 1965