Question

The number of people attending graduate school at a university may be

modeled by the quadratic regression equation y = 8x2 - 40x+6, where x
represents the year. Based on the regression equation, which year is the best
prediction for when 1206 people will attend graduate school?
A. Year 15
B. Year 18
C. Year 24
D. Year 20

Answer 1

15 years

Explanation:

Given the quadratic regression model:

y = 8x² - 40x+6 ; where

y = Number of people attending graduate school ;

x = number of years

The value of x when y = 1206

The equation becomes :

1206 = 8x² - 40x+6

1206 - 6 = 8x² - 40x

1200 = 8x² - 40x

Divide through by 8

150 = x² - 5x

x² - 5x - 150 = 0

x² - 15x + 10x - 150 = 0

x(x - 15) + 10(x - 15)

x - 15 = 0 or x + 10 = 0

x = 15 or x = - 10

Number of years can't be negative,

Hence, x = 15 years