Question

The function y = -2.38x2 + 45.24x + 800 models the population of a local high school and x = 0 represents the year 1985. Use the Quadratic Formula to estimate the years in which 1000 students attended this high school?

Select one:
a. 2017 and 2032
b. 2010 and 2019
c. 1990 and 2010
d. 1992 and 2017

Answer 1

@maths911

Answer 2

1992 is right but not 2017

Answer 3

\(\large \begin{array}{rrll}
y = &-2.38x^2 + 45.24x + 800
\\ \quad \\
{\color{red}{ \textit{population of a local high school}}}=&-2.38x^2 + 45.24x + 800
\end{array}
\\ \quad \\
\bf {\color{red}{ 1000}}=-2.38x^2 + 45.24x + 800\implies {\color{blue}{ 2.38}}x^2{\color{red}{ -45.24}}x{\color{green}{ +200}}
\\ \quad \\

x= \cfrac{ - {\color{red}{ b}} \pm \sqrt { {\color{red}{ b}}^2 -4{\color{blue}{ a}}{\color{green}{ c}}}}{2{\color{blue}{ a}}}\)

Answer 4

hmm kinda forgot the 0... well \( \begin{array}{rrll}
y = &-2.38x^2 + 45.24x + 800
\\ \quad \\
{\color{red}{ \textit{population of a local high school}}}=&-2.38x^2 + 45.24x + 800
\end{array}
\\ \quad \\\\ \quad \\
\bf {\color{red}{ 1000}}=-2.38x^2 + 45.24x + 800\implies {\color{blue}{ 2.38}}x^2{\color{red}{ -45.24}}x{\color{green}{ +200}}=0
\\ \quad \\

x= \cfrac{ - {\color{red}{ b}} \pm \sqrt { {\color{red}{ b}}^2 -4{\color{blue}{ a}}{\color{green}{ c}}}}{2{\color{blue}{ a}}}\)

Answer 5

so is it c?

Answer 6

dunno... what did you get for the discriminant?

Answer 7

9662.6576

Answer 8

@jdoe0001

Answer 9

well... you can just plug in the values to see what "t" is